630 EDWARD POTTS. 



One of thefii-st discovered polyps produced larvae February 

 3rd, March 2nd, lltli, and 15tli. Another produced larvce 

 ou February 5th, IGth, and 28tb, and March 3rd. They were 

 all thrown off from the same neighbourhood in the parents, 

 and the visible process was accomplished in a few hours. 

 In every case the act was preceded by an increased opacity 

 of the lower half of the polyp, as though it became filled with 

 granules, an effect, perhaps, of the rapid segmentation of 

 nuclei in the endodermal cells (see fig, 22). The external 

 stages in their formation, often completed within a very few 

 hours, are rather suggested than illustrated in diagram fig. 

 21 mentioned above. It will be noticed that the product, 

 whatever it may be called, is not a self-sustaining duplicate 

 of the parent hydroid, but an immature individual, needing 

 entire development of its functional parts before it becomes 

 capable of ministering to its own growth or of reproducing 

 others. 



When detached the larva) rest wherever they may chance 

 to fall, changing place only as a result of the slight writhing 

 motion sometimes noticed, or of a protoplasmic, amoeboid 

 action within the surface cells. They are long, oval, cylin- 

 drical bodies, the central parts exhibiting infinite numbers of 

 yolk-like granules from which nucleated endodermal cells are 

 gradually developed, while the superfices, even before separa- 

 tion, show a continuous, clear, hyaline ectoderm. The 

 external surface seems generally smooth, but a high magnify- 

 ing power brings out, particularly near the extremities, a 

 delicate, variable cumulation, the outer convexities of minute 

 ectodermal cells. A few nematocysts can very early be 

 detected, indifferently scattered around the margin. After 

 a few days of quiescence, one extremity (Ryder says that last 

 attached to the parent, the nearest to its proximal end), 

 becomes attached to the supporting surface, and the other is 

 gradually elevated into a more or less erect position when 

 the thread cells are formed in numbers about the distal 

 extremity (fig. 24), and maturity is reached with the fully- 

 formed capitulum. 



