68 Proceedings of the 



tration of which I have given the accompanying sketches. 

 Fig. 3 shows the newly extruded ovum with yolk and shell. 

 In fig. 4 the yolk has become irregular in shape by cleavage, 

 granular, and opaque. In fig. 5 the embryo is elongated into 

 an irregular cylinder, and is encircled by a wreath of long 

 cilia, by which it is rapidly whirled round in the shell. In 

 this stage it bears a close resemblance to the embryo of an 

 annelid (Phyllodoce) when newly hatched. In fig. 6 the ciliary 



Fig. 3. Fig. 4. Ficr. 5. Fig. 6. 



® 



wreath of fig. 5 is broken up and divided into four bundles, 

 the upper part of the embryo has become hyaline, by the 

 gradual absorption of the yolk, and the tentacles have appeared, 

 as simple granular threads, and destitute of the lateral cirri 

 which adorn those of the adult. In fig. 7 (the 

 newly-hatched Cydippe) the four bundles of 

 cilia have extended themselves into short 

 bands, — a still further absorption of the yolk 

 has taken place ; and the tentacles have become 

 greatly lengthened. My observations were 

 here arrested ; all the young Acalephs died at 

 this stage, which they attained in about five 

 days. The Cydippe, when newly released 

 from ovum, is still in a low state of develop- 

 ment. I have not been able to detect in it 

 either mouth or water-vascular canals ; the 

 ciliary bands are only four in number, instead 

 of eight, as in the adult ; the tentacles are not 

 yet fringed ; a considerable part of the yolk 

 still remains to be absorbed, and is amassed at the lower 

 extremity of the animal and about the ciliary bands, where the 

 lateral tubes of the water-vascular system may be looked for. 

 In this respect it bears a remarkable resemblance to the me- 

 dusae of some of the coryne-form polypes, in several species of 

 which I have noticed that the walls of the radiating tubes, 



Fig. 7. 



