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 tlie Challenger Nemertea. That they are developed from 



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

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

 particularly evident and very distinctly \'isible in Cerehratulus 

 longijissus, 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 

 t'-c. WWWUi { ) \ formed between the intestinal cseca. In this region all the most 



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

 in the same longitudinal section. The ova of Amphiporus marioni 



Portion of a horizontal (^\ XV. fig. 15) are characterised by the presence, in addition to the 



the digestive tract, i.e., 



Fig. 6, 

 section of a Cerehratulus. 



lateral cfeca ; g.l., the genital 



jj^^ nucleus, of a round or reuiform body, which is stained dark red by 

 t'&'^ji 'ikl^umenT'and musi picrocarmiuc, and but for this offers a certain analogy to the oil-drop 

 '^"'''''"'''^" ^" fish egss, being also more refractive than the nucleus, though 



in 



-&0 



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 (PI. 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 Cerehratulus, sp. inc. (PI. XV. fig. 18), and Drepanoj^horus 

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

 each egg separately, and which is pressed into a polygonal shajje when many I'ipe eggs 

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



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

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

 thus the aspect as fig-ured on PI. 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 (XX Villa). 



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



