can follow them; and it is a curious fact, that after the movement is completed, and they are safely ensconced, the fibres are not content to rest, but still keep up a lively motion, writhing and twisting like bundles of mi

nute worms.

The tentacles all the while lie gathered closely together in the sheath, formed for them by the tube, which has been doubled upon itself inside of the cell, like the finger of a glove inverted within the empty palm. When once more ready to emerge, the opening of the cell, which has been contracted by a circular band of muscle, like the mouth of a bag drawn up with a string, relaxes and permits the ends of the tentacles to protrude. These warily search for the cause of the previous alarm, and, if no hostile movements betray the presence of an enemy, the whole bundle slowly and cautiously follows, halts a moment, and then confidently unfolds its circlet of sentient threads. The Polyzoön reasons from the impression made upon these feelers, and cannot be induced to expose itself until thoroughly satisfied, by their exquisite sense of touch, that no danger lurks near its retreat.

Strange to say these plant-like creatures, singly mere animated pouches containing stomachs, show greater nervous sensibility than many more highly organized animals. They continually surprise us by actions which exhibit caution, fear, and anger to a remarkable extent, and imply a degree of complication in their relations, both social and physical, which the simplicity of the organization, and the limited sphere of its exercise render doubly interesting to the philosophical observer.

The wonders revealed in the structure of these lovely dwellers in the perennial shadows of our fresh waters, tempt one to linger, but the history of their circulatory

and respiratory functions, and their curious modes of reproduction must be deferred until the next number.

EXPLANATION OF PLATE 3. Fredericella regina Leidy.

Fig. 1, 2, and 3. Colonies attached to pieces of bark.

Fig. 4. Magnified view of one Polyzoön. D, brown envelope, the ectocyst; E, pellucid wall of the tube and cell, the endocyst; V, funiculus; M, M', M", upper branches of the muscles, the retractors; N, N', muscles of the fold, the retentors; F, a small infolding of the endocyst, the brachial collar; G, the pointed ruffle, or calyx; H, the threads, or tentacles.

Fig. 5. Outline of the interior of part of a young specimen. Same letters as above, with the exception of B, the invaginated fold of the tube; Y, a very young polyzoön, a bud; K, the throat or œsophagus; H", cilia surrounding the mouth; K", the valve opening into the stomach, œsophageal valve; K', stomach; K", intestinal valve partly open; K", intestine; K, opening of intestine, the anus; I, disc, the lophophore; I', the little flap, the epistome; I", the mouth; S, nerve-mass.

Fig. 6. Side view of the top of a cell, with the tube and crown drawn within; letters same as before with the exception of A"", contracted orifice of the cell; L, position of muscular band, the sphincter. Fig. 7. View of the same from above.

Fig. 8. Front view, showing upper branches of the retractors, which are attached to the wall of the tube and to the disc, M" and M'.

THE FERTILIZATION OF FLOWERING PLANTS.

BY J. T. ROTHROCK.

It is now universally accepted by botanists that there exist distinct sexes in the vegetable kingdom, and that nature's method of maintaining the existence of a specific form, is to bring the male and female elements in contact. In a normal flower, the first group of organs we find inside the corolla, are the stamens; while the yellow powder, so frequently found inside of the swollen ends (anthers), is the pollen or male element. In the centre