120 



THE VOYAGE OF H.M.S. CHALLENGER. 



the changes in shape which the developing generative sac may undergo ; accordingly we 

 will now consider a few diverging peculiarities of the generative products themselves, 

 which I was able to observe in the Challenger Nemertea. That they are developed from 



the epithelium of the generative sacs has long been known ; this 



is figured on PL XV. fig. 14, in a Hoplonemertean. It was 



particularly evident and very distinctly visible in Cerebratulus 



longifissus, where it was at the same time also demonstrable that 



there is a very sudden decrease in ripeness of the generative 



products close to the tail-end, where growth in length of the 



animal is going on, and where new generative sacs are being 



formed between the intestinal cseca. In this region all the most 



different stages of ripeness of the ova may be studied side by side 



in the same longitudinal section. The ova of Amphiporus marioni 



Fl s G ecUo7of r a' "cereLaud^ff (^ -^- **§• 15 ) are characterised by the presence, in addition to the 



laterat'^ffica t ^f^the'genitoi nuc l eus > °f a round or reniform body, which is stained dark red by 



^rM^klgtmLXand'Tus^ picrocarmine, and but for this offers a certain analogy to the od-drop 



in fish eggs, being also more refractive than the nucleus, though 



not quite so highly as the latter. This paranucleus was already observed in the youngest 



eggs (PI. XV. fig. 15, a) ; at that time its relative size, when compared to that of the whole 



egg, was much more considerable. A second smaller specimen of Amphiporus marioni was 



distinguished by the same peculiarity, which may thus in certain cases help to identify the 



species, as I did not find the same feature in any other species of Hoplonemertea. 



Of the eggs of Pelagonemertes it has already been recorded that they are distinguished 

 by an investment of follicle cells (PL VIII. fig. 11) ; the development of this could also 

 be traced downwards to early stages, which were present in the same specimen (fig. 10) 

 side by side with the riper stages. 



In the Schizonemertea two facts deserve mention, although their significance cannot 

 well be discussed as long as fresh specimens are not available. The one is the pre- 

 sence round the ripe eggs in Cerebratulus, sp. inc. (PL XV. fig. 18), and Drepanophorus 

 serraticollis (PL XV. fig. 17) of a hyaline, apparently mucous layer, which surrounds 

 each egg separately, and which is pressed into a polygonal shape when many ripe eggs 

 are enclosed together in the same sac. The layer is comparatively thick. 



The second fact was observed in Cerebratulus parkeri, where the peripheral proto- 

 plasm was much more darkly stained and more coarsely granular, all the eggs having 

 thus the aspect as figured on PL XV. fig. 16. 



As to the spermatogenesis I have no new observations to record, spirit specimens 

 alone rarely presenting favourable material for such researches. These phenomena have, 

 moreover, been recently fully studied by Sabatier (XXVIIIa). 



Hermaphrodite specimens were not encountered by me in the Challenger collection. 



