The fish remained at the bottom of the aquarium and went slowly to take refuge under a tile which served as a shelter. It was then three o'clock in the afternoon. The next day at the same hour I found it in a package of Jussieua plants which was floating on the surface of the water.

In order to examine my fishes closely, I removed the plants and observed that Nos. 1 and 2 did not appear to be at all influenced by the operation which they had undergone. Only No. 2, deprived of its pectoral and ventral fins, seemed unable to move easily. No. 3 moved the posterior portion of its body quickly, and by uninterrupted lateral shakes was able to turn, rise, fall and swim forward,. but with much less rapidity and ease than the others, which, with a stroke of the tail, darted like arrows without needing to strike the liquid again in order to advance.

The third

fish ended by learning to replace his caudal by the movements of the dorsal and anal, which increased a little in size, doubtless from the exercise.

One more experiment remained to determine the functions of the fins and of the airbladder. All the fins except the caudal were cut off of one fish. The creature thus mutilated at first appeared undecided, like No. 3, and moved slowly at the bottom of the aquarium; but the next day I saw him swim rapidly and execute with agility all his usual evolutions. The only noticeable peculiarity was that in order to keep himself in position he caused his only fin to vibrate rapidly and constantly, and that these vibrations communicated a trembling to the entire body. The equilibrium was, therefore, still preserved, and the air-bladder did not cause the fish to turn belly upwards, although he maintained himself at the bottom of the water, in the middle or at the surface, experiencing in consequence a series of different pressures. My friend, the learned Belgian professor, F. Plateau, so well known by his experiments on insects, and who encouraged me to publish these studies, writes to me that he teaches his pupils that locomotion in most fishes is effected by flexions of the entire caudal portion of the body, and

that the undulations of the odd fins (dorsal, anal and caudal) serve only to give more precision to the general movements of locomotion; and that, save in exceptional cases, the functions of the pairs of fins are almost inappreciable. I am happy to see my observations accord with the ideas of a savant whose name carries weight.

When my fishes swim slowly or remain motionless, the caudal fin executes very clean helicoid movements (skulling). This fin appears, therefore, to be, not indispensable, but extremely useful in swimming. Progression forward is due to the alternate flexions of the tail, that is to say, of the part of the body situated behind the anus, as everybody knows; but, according to the observation made on No. 3, it is evident that the fin which terminates it lends it a very powerful aid, for both rapidity and uniformity of motion. With regard to the function of the pectorals, I have remarked that when the fishes which possessed them remained stationary they, nevertheless, continued to move these fins rapidly, and that the latter appeared to be intended to produce currents in the water to renew the portions of this fluid which had already yielded their oxygen to the gills and remained charged with carbonic anhydride.

It is evident that these experiments on a single species and on so small a number of fishes are insufficient to determine in a general manner the rôle of each kind of fin, and I publish them only to instigate other more varied studies, particularly by means of fishes provided with well-developed fins. With regard to those vertebrates which possess only the caudal, it is known that the shape of their body, especially of the posterior portion, perfectly explains direct progression.

Before closing this article, I wish to call attention to a fact which perhaps has not yet been observed, or at least not published. The amputated dorsal fin and the two pectoral fins have grown out again to a great extent. It is probable that the mutilated fishes continued mechanically to make use of the stump which remained to them, doubtless with a small fragment of the fin, and that under that action the

rest of the organ reproduced itself. What would seem to prove it is the fact that, as I have said in speaking of No. 3, the dorsal fin increased in size on account of the use he made of it to replace the amputated caudal fin. A. DUGÈS.

GUANAJUATO, MEXICO, April, 1905.

LABORATORY EXPERIMENTS WITH CS, TO DETERMINE THE LEAST AMOUNT OF GAS AND THE LEAST TIME REQUIRED TO KILL CERTAIN INSECT REPRESENTATIVES OF VARIOUS FAMILIES.1

Ex

WHILE a sufficiently large series of insects has not yet been worked upon to draw a definite conclusion upon the above point, the following paper is submitted as showing some interesting results incident to this work. periments were begun in California a few years ago, and continued for a time in Minnesota. Three hundred and eighty-six insects have been tested. Of this number some have not been included in the tables, where the record was not regarded as sufficiently complete.

The points which might be brought out by an exhaustive series of observations in this line are as follows: Least strength required with a minimum expenditure of time to kill (a) insects in general, (b) particular groups, safety to foliage being understood; effect of moisture upon results; effect of temperature upon results; expense of material for effective use upon a known number of plants, trees, insect colonies or stored products, what per cent., if any, succumbed after seeming recovery; beginning effects of gas upon (a) insects in general, (b) groups in particular; significance of occasional spasmodic movements of legs, wings, sometimes long after apparent death; corroboration of laboratory results with results from the field as far as possible; different results with different brands of CS,; corroboration with previous published state

ments.

Method and Apparatus Described; Compu1Abstract of paper read before the Association of Economic Entomologists at Philadelphia at their last annual meeting.

tation. The necessary crudity of the apparatus and method described is evident, and must render the results in the case of insects of any size not even approximate. An insect as large as Ectobia, or Apis mellifica, for example, or the larva of the western peach-tree borer, or that of the Mediterranean flour moth, evidently displaces so much of the gaseous contents of a vial when introduced, as to render absurd the proportions of gas to atmosphere as given. Even in insects smaller than these there is undoubtedly an error due to displacement, yet the writer believes that the method described here comes as near demonstrating facts in this connection as possible, particularly in the case of very small insects, and it has certainly brought out interesting results, from which we may select what appears authentic.

A large number of homeopathic vials were secured, of the same size (homeopathic 2 gram vial No. 1,657 with patent lip), also pieces of flexible rubber piping of such a size as to fit tightly over these vials. Into one vial a drop of CS, was allowed to fall from a medicine dropper, and the mouth of this vial immediately placed against the mouth of another empty vial, the rubber tubing referred to serving to hold the two vials closely together, and preventing any egress of gas, or entrance or exit of atmosphere.

The average capacity of these vials was 8.7 c.c., and it was upon this basis that our calculations were made. The volume of gas coming from one drop of CS, equaled 4.35 c.c., and, therefore, filled half a vial.

It is evident, therefore, that the union of the first two bottles, made immediately, before the gas had an opportunity of driving out any of the atmosphere, caused a mixture of one part of gas to four of atmosphere; the second change, one to eight; the third, one to sixteen; the fourth, one to thirty-two, etc., or, interpreting it with reference to the liquid volume of CS, to the atmosphere, we find that the union of the first two bottles equaled one part of liquid CS, to 1,494 parts of atmosphere, or in round numbers, 1,500 parts of atmosphere; the second change, one part of liquid CS, to 2,988 parts of atmosphere, or in round num

first marked uneasiness on the part of the insect under treatment. In some cases this effect is immediate.

It is to be also noted in this particular that in the case of many specimens the first noticeable effect was an attempt on the part of the insect to clean its antennæ. The striking individual variations, in other words, the revival of many subjects after apparent death, show the necessity of extreme thoroughness in field and greenhouse, that is, a long enough exposure to insure carrying the insect beyond all possibility of recovery.

One hour's exposure to one part liquid CS, to 12,000 parts of atmosphere is apparently sufficient to kill aphids, but in making suggestions for practical application, I should certainly urge an hour and a half's exposure to that strength as being more sure, especially with crude CS,. Ants appear generally to succumb to one hour's exposure to one part liquid CS, to 12,000 parts of atmosphere, the same as aphids, and yet in actual practise, to insure the best results, they should be subjected to a longer treatment. Aphids show immediately the effect of exposure, and some were on their backs from two to four minutes after treatment, and yet recovered after an exposure of three fourths of an hour to one part liquid CS, to 12,000 parts of atmosphere. Tribolium confusum was observed particularly to clean the antennæ immediately upon exposure.

The remarkable vitality of the Aphidæ (insects that we commonly regard as extremely delicate) is to be noted in connection with this work. Further, in a few cases we found that some of the insects which recovered such treatment died later, say within twentyfour hours, although the bottles in which they were confined were left open, only slightly plugged with absorbent cotton. This 'apparent death' is very deceiving. pearances these insects were absolutely dead, perfectly motionless, and in many cases we entered them on the record as dead, although we had to change that record several minutes later, when a wing, a leg or an antenna would be seen to move. Frequently only a slight

To all ap

So then in practise it will be necessary to calculate from the formula only one of these probable errors for a given distribution, viz., the probable error of the skewness. Having determined this we need only to multiply it by 2, by 4 and by σ to obtain the values for the other three. RAYMOND PEARL.

BOTANICAL NOTES.

HALLIER'S NATURAL SYSTEM.

In the July number of The New Phytologist Professor Dr. Hans Hallier discusses further his provisional scheme of the phylogenetic system of flowering plants. The general features of his system are: (1) the Angiospermae constitute a monophyletic group; (2) the · Amentaceae are not an old type remaining in a lower state of development, but as 'the highest and most reduced types of one of the lines of Dicotyledons'; (3) they and all other lines of Dicotyledons have been developed by reduction of flower and fruit from the Polycarpicae, the latter group being derived immediately from Bennettitaceae or other extinct Cycadales; (4) in the same manner, the Liliiflorae and all other syncarpous Monocotyledons have been derived by union of the carpels, by reduction in the number of parts, by epigynous insertion of the perianth, and by other changes in the structure of flower and fruit from the polycarpous Monocotyledons (Helobiae), which latter group originated from the polycarpous Dicotyledons (Polycarpicae and Ranales); (5) the Apetalae and Sympetalae are unnatural groups.

In applying these general principles, Dr. Hallier has worked out the following arrangement of the Dicotyledons, which he distinctly says is provisional for all after the Piperales. 1. POLYCARPICAE (Magnoliaceae, Canellaceae, Anonaceae, Myristaceae, Calycanthaceae, Monimiaceae, Lauraceae).

2. RANALES (Berberidaceae, Menispermaceae, Ranunculaceae, Nymphaeaceae, Ceratophyllaceae).

3. RHOEDALES

aceae, Resedaceae, Cruciferae).

* *