130 LECTURE VII. 



indivisa, also, the sperm-capsules repeat the grape-like arrangement 

 and situation of the ovicapsules. In Etidendrium racemostim the 

 sperm-capsules are moniliform, and are supported on particular stems ; 

 the outermost capsules, which first appear, contain the best developed 

 spermatozoa. These sperm-capsules were distinguished by Cavolini, 

 as " uova a corimbo,'' * from the ovicapsules, which he called " uova 

 a racemo."f The distinguished Neapolitan zoophytologist also re- 

 marks that each kind of capsules occur in different individuals ; and 

 Krohn, to whom science is indebted for a determination of the true 

 nature of the " uova a corimbo," found as a general rule that the 

 sperm-capsules were developed in the Eudendrium racernosum, the 

 Plnmularia cristata, and Sertularia misenensis, on particular indi- 

 viduals or compound groups of individuals, the ovicapsules being 

 developed on other such individuals. 



The true ovum of the Hydrozoa has its germinal vesicle and spot, 

 and after impregnation the germ-mass is formed by spontaneous 

 fission of the germ-cells and cleavage of the granular yolk, as in the 

 ova of the Ascaris (p. 113.). 



In the Hydra this process goes on before the ovum quits the 

 parent, and before it has acquired its bristled chorion. In the marine 

 species the young may escape from the ovicapsule in the condition 

 of ciliated locomotive bodies, called " planulae" by Dalyellif; or the 

 planultB may be hatched in the interior of a polype-individual de- 

 veloped from the summit of the ovicapsule, and which, after liberating 

 them, may wither and fall like the flower of a plant § ; or a generated 

 individual of a particular form, such as e. g., the Medusa octocilia and 

 M, duodocilia of Dalyell ||, developed from Eudendrium i-amosum, and 

 the Tintinnahulum or Bell-medusa observed by the same author as 

 the progeny of the Campamdaria dichotoma, may be developed in 

 and escape from the ovicapsule, and, by its own power of locomotion, 

 carry the contained ova to a distance from the composite and fixed 

 group of nutritive individuals. The ova may be developed within 

 the bell-shaped Acalephoid prior to its detachment, as in the Coryne 

 vulgaris, observed by Wagner, or not until it has become detached 

 and acquired the full characters of a bare-eyed Medusa. 



The phenomenon of the development of a polype-like larva in the 

 vesicles did not escape the keen eye of Ellis. He says, " I first per- 



* CVI. tab. vi. fig. 14. t CVI. tab. vi. fig. 6. 



% CIX. p. 150. pi. xxiv. (Sertularia abietina), p. 162. pi. xxix. (Sertularia 

 halecina). 



§ CXII. p. 259. tab. vi. fig. 13. {Campanularia geniculata). 

 II CIX. pl.xi. figs. 9 and 11. 



