ORGANS OF CAMPANULARIA GENICULATA. 65 



When the spennatozoids have been evacuated in the natural 

 way, the polype-like envelope contracts and ultimately dis^ 

 appears altogether, the next highest of the remaining globules 

 in the meanwhile escaping in succession. Capsules occur 

 with four or five polypoid envelopes attached externally, some 

 of which, however, are always close upon disappearing. 



Of the vessels, which Loven has figured in the precisely 

 similar egg-tunics seated upon the ovi-capsules, but which I 

 have never been able to perceive in these tunics, no indica- 

 tions exist in the spermatic envelopes just described. 



The male and female capsules are always placed upon 

 different polypidoms, so that the semeji has frequently a con- 

 siderable distance to traverse in order to reach the ova to be 

 impregnated. It may thence be concluded, that in sea-water 

 the spermatozoids do not speedily lose their motility and 

 capability of impregnation. I was still able to perceive the 

 movements of the spermatozoids an hour after their liberation. 



That an impregnation by the semen is indispensably requi- 

 site for the development of the ova, I have frequently satisfied 

 myself, since it was only the ovi-capsules which had been 

 associated with 7nale polypidoms in a glass of water, that 

 afforded embryos ; whilst in those which had been kept apart, 

 the ova, after entering the polypoid tunics from the ovicell, 

 were always dissolved. The process of segmentation com- 

 menced in them, but soon remained stationary, and never 

 reached the formation of an embryo. This fruitless process 

 of segmentation taking place without impregnation was also 

 noticed and figured by Loven, but erroneously explained. He 

 regarded it as a spontaneous division of an embryo for the 

 purpose of multiplication, and believed that each separate cell 

 would become an embryo. 



Lister's drawing and description (Phil. Trans. 1834, PI. X. 

 Fig. b 4, p. 376), cited by Loven on this point, and regarded 

 by him as indicating the same thing as this futile division of 

 the embryo, admit, as it appears to me, of a totally different 

 explanation. The figure indisputably shows that Lister had 

 seen the male capsules and the escape of the spermatozoids ; 

 but he had no notion of the meaning of what he thus ob- 

 served. 



With regard, lastly, to the polypoid envelope of the sper- 

 matic globules, it corresponds in all respects with the analo- 

 gous tunic of the ova and embryos. 



If the latter is to be regarded as the analogue of the free 

 medusiform offspring of other Campanularice so also is the 

 former — the tunic of the spermatozoids. I have already said 

 that the decision of this question cannot be expected without 



VOL. III. F 



