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of these, is invalid and its type, D, becomes the proper type of X. This is the simple But let A and C

condition of the problem.

be set off to form a new genus; C and D, another. Let a new genus be formed which would probably include B in it. Let still another be framed which might possibly include D. Let it be further uncertain whether A and B should be placed in different groups. Let still another writer definitely connect the old genus with A, while another uses it, not for any of its constituents, but for some new form probably congeneric with B, and you have a not unusual statement of the problem.

There is no way out of this by the rule of elimination. By accepting the first reviser rule, itself subject to the Linnæan rule and the rule of tautonomy, we may well fall back on the rule of page precedence, and let the rule of elimination be simply a recommendation to the first reviser, without direct validity of its own. This is the position of the rule of elimination in the new International Code.

I give two concrete illustrations of the difficulties of the rule of elimination among genera of fishes.

The genus Clupanodon Lacépède, 1803, was based on toothless herrings,' the chef de file being Clupanodon thrissa. This species as described by Lacépède, is the Clupea thrissa of Broussonnet, the American species, later called oglinus by Le Sueur. This is, however, not the original Clupea thrissa of Linnæus, 1758, which was based on the Clupea thrissa of Osbeck, 1757, a Chinese species, later called Clupea nasus by Bloch, a species of Konosirus. The second species of Lacépède, nasicus, is the same as Clupea nasus of Bloch. The third, pilchardus, is the Clupea pilchardus of Linnæus, a species of Sardinia, which is probably the same as Sardinella. The fourth species of Lacépède, sinensis, is apparently the species called later Clupea ilisha, and is probably not the original sinensis of Linnæus. is a species of Clupeonia or Harengula. The fifth, africanus, is a species of Ilisha, and the sixth, jussieui, is the original type of the genus Clupeonia.

It

Arranging these according to the modern

genera:

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Opisthonema Gill, 1863, based on thrissa of

Lacépède oglinus of Le Sueur. Konosirus Jordan & Snyder, 1900, based on punctatus Schlegel, which is a congener of Clupea thrissa Linnæus (= Clupea nasus Bloch) and not of Clupanodon thrissa Lacépède, which is oglinus of Le Sueur. Most writers unite Konosirus with Dorosoma Rafinesque, 1829; but the two are probably distinct.

2. nasicus. This is the original thrissa of Le Sueur and is congeneric with Konosirus punctatus. 3. pilcharus. This has never been made type of a genus. It is certainly congeneric with Sardinia Poey, 1870, with Amblygaster Bleeker, 1855, and I now think with Sardinella Valenciennes, 1845. Most writers (wrongly I think) unite all these with Clupea Linnæus, 1758.

4. sinensis. This is referred by Valenciennes to Clupeonia Valenciennes, 1845; which genus is probably identical with Harengula Valenciennes, 1845, earlier page. Most writers (I think wrongly) place it in Clupea.

5. africanus. This is congeneric with the type of Ilisha Gray, 1836, and with that of Pellona Valenciennes, 1845. It has never been taken as type of a genus.

6. jussieui. Type of Clupeonia Valenciennes, 1845, apparently congeneric with types of Harengula and Kowala of the same author on earlier pages. Usually referred to Clupea. By the first reviser' after Lacépède, Rafinesque, 1815, Thrissa is substituted for Clupanodon, and Lacépède's thrissa is doubtless to be taken as Rafinesque's type. By the next, Buchanan, 1822, ilisha (= sinensis Lac.) is described as a new species of Clupanodon. The genus Clupanodon then dropped out of notice until revived by Dr. Jordan in 1882, by a process of elimination for Clupeonia jussieui. Later the same writer, by another process of elimination, substituted Clupanodon for Sardinia. Still later, by the same process with further light, the newly defined genus Konosirus, being congeneric with Clupanodon

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platessa (type of Platessa Cuvier, 1817). flesus (type of Flesus Moreau, 1873, a genus very close to Platessa, perhaps, in fact, identical).

limanda (type of Limanda Gottsche, 1835). solea (type of Solea Quensel, 1803, of Solea Rafinesque, 1810, and of Solea Cuvier, 1817). rhombus (type of Rhombus Cuvier, 1817, name preoccupied of Rhomboides Goldfusz, 1820, substitute name; also, as Bothus rumolo, the first species named under Bothus Rafinesque, 1810).

maximus (type of Psetta Swainson, 1839, not Psettus Cuvier, 1817; first species named of Scophthalmus Rafinesque, 1810, which includes also rhombus).

passer (a synonym of flesus).

Scophthalmus and Bothus are based on three species each, the two categories being essentially the same, Scophthalmus being based on literature, Bothus on specimens. But the order is changed in the two cases, maximus occurring first under Scophthalmus,

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The

The first reviser, Rafinesque, 1810, leaves no species in Pleuronectes, unless, as he refers all the other species to other genera, we might regard hippoglossus, which is not mentioned by him as the type of his Pleuronectes. next reviser, Cuvier, 1817, recognizes the genus, Pleuronectes as used by Linnæus, but at once separates it into four genera or subgenera dropping the original name. These are Platessa (platessa, flesus, limanda), Hippoglossus (hippoglossus), Rhombus (maximus, rhombus) and Solea (solea). Meanwhile Solea had been set off previously by Quensel (1803) and by Rafinesque (1810), the latter author very erroneously referring to it, platessa, flesus and limanda also. Swainson, 1839, the next reviser, recognizes Pleuronectes (platessa), Hippoglossus (hippoglossus), Psetta (maximus) and Solea (solea). This is the first restricted use of Pleuronectes since the time of Linnæus and his followers. Later Pleuronectes was restricted by me to maximus by the rule of elimination, flesus being then regarded, as it is still regarded by most authors, as congeneric with platessa. Limanda is also near platessa. But neither limanda nor flesus is the best known European species' of the Linnæan genus Pleuronectes. The rule of the first reviser would fix Pleuronectes with platessa, the rule of the best known species with platessa or maximus, the rule of elimination would place flesus as type of Pleuronectes, if defined as dealing with a species at a time. But Rafinesque took out solea, platessa and flesus together, to form his genus Solea, leaving only hippoglossus not provided for. This fact, some would hold, restricts Pleuronectes to P. hippoglossus. Cuvier next took out all the species, leaving no genus Pleuronectes, and placing Rhombus last, next to Solea. On the other hand, platessa was placed first by Cuvier, its subgenus Platessa being apparently the chef de file subgenus in Cuvier's genus Pleuronectes.

With this group nothing in particular can

be settled by the process of elimination unless we agree beforehand as to whether Flesus is a valid genus, or as to what were the unexpressed purposes of Rafinesque.

But common usage and common sense agree in placing platessa, the common Plaice, as the type of Pleuronectes.

DAVID STARR JORDAN.

AN INTERESTING CRETACEOUS CHIMEROID

EGG-CASE.

ALMOST nothing is known of the structural characteristics of the holocephalous fishes of the Mesozoic period except dental plates or teeth. The remains of such, however, are numerous and about a score of generic names have been proposed for them, although A. Smith Woodward only fully recognizes five, Ganodus, Ischyodus, Edaphodon, Callorhynchus and Elasmodectes. I was, therefore, much interested in a fossil which Drs. Frank H. Knowlton and T. W. Stanton referred to me for identification, if possible, and which I at once recognized as a chimæroid ovicapsule apparently most nearly resembling that of modern deep-sea forms.

The

The interest arises from the assumption that where likeness prevails between such products, not only the parts which frame them but other structures must correspond. inference is not irrefragable, but in the absence of contradictory data, perfectly legitimate as a provisional hypothesis at least.

The fossilized egg-cases previously known are few and the indications as to affinities interesting as well as important. Three figures have been published of Jurassic eggcases, two by Emil Bessels and one by Otto Jaekel. All are of the Callorhynchus type and it is significant that a 'right palatine tooth,' obtained from the Lower Greensand' of New Zealand, has been attributed by E. T. Newton and Woodward to that genus and named Callorhynchus hectori.

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The newly found fossil was obtained by Mr. N. H. Darton, of the U. S. Geological Survey, from 'massive sandstone' a few miles west of Laramie, Wyoming.

The contour and general form are well preserved but not the details. The resemblance

to the ovicapsules of Harriotta and Rhinochimæra lies in the absence of differentiation between the anterior and posterior portions of the lateral alæ of the capsule and the uniformity of the transverse costal ridges all through. It differs from the ovicapsules of both Harriotta and Rhinochimæra by the greater width of the alæ and especially the greater width and extension forward along the sides of the archidome.' The resemblance is greatest to Rhinochimæra.

The genus Harriotta was set apart as the type of a subfamily (Harriottina) by Gill, in 1896, and it was associated with Rhinochimæra in a family (Rhinochimærida) by Garman, in 1904. It is to this group (if a family, properly nameable Harriottida) that the Wyoming fossil belongs. It can not be correlated with any one of the many generic names (Eumylodus, Mylognathus, Dipristis, Sphagepæa, Diphrissa, Bryactinus, Isotonia and Leptomylus) that have been especially coined for American Cretaceous fossils, but the naming of it, if such must be done, I leave to Dr. Dean who is now publishing (through the Carnegie Institution) an elaborate work on the chimæroids. I have had the privilege of looking over the proof-sheets of that work and my knowledge of the ovicapsules of the Harriottidæ is chiefly derived from it, though I had long ago seen those of Harriotta.

If these determinations prove correct and the groups named families by Garman are accepted as such the curious deduction follows that no fossil ovicapsule of a typical chimærid has been found as yet.

Although the living harriottids are deepsea forms, it does not follow that a deep sea is indicated for the habitat of the extinct harriottid. The character of the sandstone as well as of the basin in which the ovicapsule was found is opposed to the hypothesis of a deep sea. It must be remembered, too, that the same genus may have species ranging from shallow water to abyssal depths; Chimæra, for example, has a species (C. colliei) which may be caught from a city wharf and

In the interest of conciseness of description I would use archidome for the chamber for the head and trunk of the chimæroid and urodome for that receiving the caudal portion.

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moved by a screw, thus making pressure on the mercury column. The end of the capillary dips in a reservoir containing 20 per cent. sulphuric acid. A little mercury is placed in the reservoir. Platinum wires lead from this and the mercury in the capillary to convenient binding posts. When mercury is placed in the vertical tube it enters the capillary until the weight of the column of mercury is balanced by the surface tension. If the capillary be now dipped in the reservoir containing the sulphuric acid and the piston driven upward by its screw, mercury will be forced out of the capillary into the acid, and on lowering the pressure the mercury will retreat within the capillary, drawing the acid after it. As the

mercury in the capillary is kept from falling by the surface tension, it is obvious that whatever increases or diminishes the surface tension, for example an electric current, will raise or lower in corresponding measure the mercury in the capillary. The alteration in surface tension is accompanied by the movement of ions between the meniscus and the remaining electrode of the electrometer (the mercury in the acid reservoir). In practise it is found that this movement can be neither very rapid nor long continued, without injuring the sensitiveness of the instrument. The potential difference from even a single element (Daniell or dry cell) is far too large to be used safely. It is advisable to employ a potential divider, or rheochord, which shall permit only a fraction of the original potential (not more than 0.1 volt) to reach the electrometer.

The electrometer should be kept short-circuited, except during an observation, so that the capillary and the mercury in the reservoir may always be connected through a conductor. The short-circuit key is shown in Fig. 1. A strip of spring brass connected with one of the binding posts of the electrometer rests against a second piece of brass connected with the other binding post, except when depressed by the finger. The point of higher potential, when known, should always be connected with the capillary.

When the capillary electrometer is connected with two points of unlike potential the meniscus is displaced. The pressure necessary to bring it back to its original position is proportional to the electromotive force that displaced the meniscus. Thus by connecting the electrometer with known differences of potential it may be experimentally graduated. In practise, the relation between the pressure and the potential must frequently be redetermined. It is usually easier to measure differences of potential, such as the demarcation current of nerve or muscle, by compensation. In this method the electromotive force of the demarcation current is measured in fractions of a Daniell cell, or any other constant element, by bringing into the same cir

cuit with the current of injury, but in an opposite direction, so much of the current from the cell as will exactly balance the current of injury, i. e., so much as will keep the meniscus of the electrometer from moving in either a positive or a negative direction when connected with the circuit.

Numerous advantages are presented by the form of electrometer here shown. It fits the stage of the microscope. The microscope need not be tilted very far, and the observer is therefore in a comfortable position. The position of the electrometer on the stage may readily be changed. All the parts near the acid are of hard rubber, thus excluding currents that might arise from acid touching metal parts. The acid tube is flanged so that the acid can not creep out along the capillary tube. The capillary can easily be brought against the wall of the acid tube. The tube from which the capillary springs descends. within the acid tube, thus protecting the capillary against breakage. Either tube may at once be removed from its holder. The platinum wires extend to the binding post, and are not simply short pieces soldered to copper wire. The wire to the capillary tube extends to the bottom of the tube, thus maintaining the contact until all the mercury in the tube is used.

About one cubic centimeter of paraffin oil should be placed above the piston. Only absolutely clean double-distilled mercury should be used. W. T. PORTER.

HARVARD MEDICAL SCHOOL.

QUOTATIONS.

RESEARCH WORK IN GREAT BRITAIN.

EXPLAIN some remarkable discovery of pure science to the ordinary man and he instantly wants to know what is the use of it or casts about for some way of utilizing it for profit. He neither understands very clearly how the discovery was arrived at nor the importance it possesses apart from immediate application to the meeting of daily wants. Yet nothing is more certain than that the applications of science which most fully subserve the wants of man depend in every considerable case upon

the results obtained by men who had no practical application in view. He who finds out merely for the sake of finding out everything that can be known about a given subject has so far contributed to laying the foundations of advance as it is understood by the practical man. Without the discoveries thus made the practical man finds himself balked at every turn. For practical applications depend upon the combination of a great many factors, anddemand a power of selection from a vast body of ascertained facts which are supplied only by the seeker after knowledge for its own sake. Of the knowledge thus acquired no man can say what part will be first utilized, or how long any portion may remain useless for practical purpose. That depends very much upon the progress made by research in other directions, hence many important results have been lost to sight merely because some link was missing in the chain connecting them with other known facts. In that case they have to be rediscovered, otherwise they in turn become the missing links, and for want of them other knowledge remains sterile.

Now it is too true that in this country, as Professor Nuttall complains, research is not a career. Pure science does not bring bread and butter. This country has often been fortunate in having men of means who devoted themselves to research for the love of truth, and it has had men like Faraday, of great simplicity of life, who were not merely content, but glad, to live on the income of a clerk while making discoveries that subsequently changed the face of society. But we can not depend upon a constant and adequate supply of either type. The field is now very large and very costly to work. There are many temptations to turn aside which we must expect to be too much for most men who do not possess compelling genius. Hence, if we do not provide a living wage and adequate equipment for a sufficient number of seekers after knowledge, we must expect to be beaten in practical affairs by nations which better understand their true interests. The London school loses promising men who go into practice. In one way or another every branch of research loses promising men, who either go into

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