626 Transactions of the Society. 



with its own stomacli driven right through its mouth, so that its 

 own trochal disk appeared half- way down its body. In fact the poor 

 creature had almost been turned inside out in being suddenly thrust 

 through the vagina. 



The ephippial eggs are often of a yellow colour, and theu' out- 

 most covering is corrugated very similarly to the ephippial eggs in 

 A. Sieholclii. 



Muscular and Vascular Si/stems. — These in the female are 

 very similar to those in the male, but are much better seen in the 

 latter, owing to the absence of the stomach and to its greater trans- 

 parency. 



The Male. 



The male is rather more than half the size of the female, and 

 when full grown is about 1-3 3rd in. in length. I'he largest 

 female I have seen was rather less than l-20th in. The teeth and 

 mouth, with their inclosing ring, the pharynx, oesophagus, gastric 

 glands, and stomach are all entirely wanting in the male, which has 

 as it were in lieu of them thi-ee or four rounded masses adhering to 

 the dorsal surface in front of the dorsal hump. These are structure- 

 less, faintly opaque and granular, and their use is unknown. 

 Possibly they may be a kind of stored-up material to compensate 

 in some degree for the male's inability to take nourishment. 



Rep'oductive System. — The penis and sperm-bag are shown in 

 situ in fig. 3, and much enlarged in fig. 6. The former is a canal with 

 delicate longitudinal furrows, and lying sheathed in soft granular 

 masses. Its obliquely cut opening is ciliated. 



It can be drawn backward by two pairs of muscles that are 

 attached by their broader ends to the dorsal surface near the bases of 

 the dorsal muscles ; and by their otber extremities to the posterior 

 end of the penis. Short muscular threads help to draw the penis 

 forward, but I think that this motion is mainly caused by the vigorous 

 compression of the whole body by its transverse muscles. The 

 spermatozoa can be distinctly seen in motion within the sperm-bag, 

 and they are of the two forms drawn in fig. 7. 



I attempted on several occasions to see the union of the sexes, but 

 without success. The male would jilay round a female, and thrust 

 the penis backwards and forwards, but I never observed any copu- 

 lation. Once I found the male adhering by the tip of the penis to 

 the female ; but it was on the outside of the centre of the ventral 

 surface, and not at the opening of the oviduct. 



Vascular System. — A. Brightivellii, A. Sieholdii, and A. Ebbes- 

 hornii all differ from A. priodonta in the large size of the contractile 

 vesicle. In the female of A. Ebheshornii this sometimes swells till 

 it appears to occupy nearly two-thirds of the body-cavity. In the 

 male it is much smaller, but in both sexes it is covered with a fine 



