268 BULLETIN OF THE 



day after the capture of the adult. It is seen in a little different plane 

 from the preceding, but in such a way that the organs already mentioned 

 can be easily distinguished. We have in this stage an addition of most 

 important character, for at this time first appears the beginning of the 

 polypite. The larva is shown in such a way that the embryo is twisted 

 somewhat as compared with former stages, and the hj-di'ophyllium has 

 its proximal edge so turned into view as almost completely to cover the 

 yolk. By this new position of the larva the conical end of the primitive 

 cavity near the float is well shown, while the two buds which later form 

 the serrated hydrophyllia are thrown to one side. The most devel- 

 oped of these last-mentioned organs has a spatulate form, and shows the 

 three layers, epiblast, middle layer, and hypoblast, as well as a cavity 

 which occupies most of the interior of the organ. The other hydrophyl- 

 lium is not as well formed, and is more highly colored. 



In addition to the buds which have been mentioned as already formed, 

 we have represented in this stage a significant thickening (pyt.) at one 

 pole of the two layers which surround the yolk of the egg. This pole 

 is situated in a point at right angles to that where the bud which forms 

 the float first appears. The elevation of these two layers takes the form 

 of a simple bud comparable with other buds of the primitive larva, and 

 xiltimately forms the first or primitive polypite of the Agalma. The 

 elevation of the primitive polypite is reddish yellow and ciliated, with 

 the lower layer slightly separated from the cells of the yolk. Although 

 the point at which the polypite in Agalvia develops is very difterent 

 from that at which the same organ of Crystallodes, as recorded by Ha^ckel, 

 arises, these differences are not too great to have a similar morphological 

 interpretation. Like all organs or parts of the Agalma body, the poly- 

 pite originates as a three-layered bud from the surface of the yolk. Like 

 them also it separates from the yolk-cells, leaving a cavity between the 

 hypoblast and vitelline cells. A part of those walls of the yolk which 

 enclose the yolk-cells becomes the outer wall of the float ; another part 

 is modified into new buds, which develop into tasters, hj'drophyllia, and 

 tentacles; and still another part forms the walls of the first-formed po- 

 lypite. Can we not consider that the yolk-sac in this case, as in Crystal- 

 lodes, is not changed into the polypite, as in Physophora and some other 

 genera % 



From Fig. 16, PI. III., taken five days after the capture of the Agalma, 

 we may obtain a somewhat better idea of the relationship between the 

 buds which form the float, the serrated hydrophj-llia, and the first-formed 

 polypite. In the view of the larva as here seen, we are looking at the 



