134 w - c - CURTIS. 



accomplished and show the characteristic attitude of the proglottid 

 from a front and side view. 



Proglottids which have thus stripped themselves of their eggs 

 may continue to live in sea- water for a day or two, but I have 

 not experimented with them to ascertain how long their existence 

 may be prolonged. 



The rupture of the uterus may be very readily produced in a 

 proglottid having any considerable accumulation of eggs, if a 

 little pressure is applied with a cover-glass or otherwise. But 

 the process above outlined is something brought about spon- 

 taneously by the proglottid itself after it is transferred to sea- 

 water. Proglottids which have been artificially compressed in 

 killing, for whole preparations almost always have the uterus rup- 

 tured and the eggs discharged. They then present the appear- 

 ance shown in Fig. I, of a large oval hole opening into the 

 uterus cavity, while the boundaries of the latter can be traced as 

 a very delicate outline still conforming to the general outline of 

 the full uterus. A proglottid which is in the last stages of egg- 

 laying after the spontaneous rupture of its uterus shows the same 

 sort of opening, but perhaps more widely distended. Such 

 specimens which were killed without compression are shown in 

 Figs. 6 and 7. 



My observations are then that the proglottids when large and 

 having the uterus full of eggs (Figs. 2 and 5) will, by a quite 

 definite series of muscular contractions and writhings, rupture the 

 nipple-like prominence at the summit of the protruding uterus 

 (Fig. 5) and allow the eggs to gush forth, the proglottid con- 

 tinuing its writhing movements in a less pronounced degree even 

 after all the eggs have been shed (Figs. 6 and 7). The fact 

 that this egg-laying occurs immediately after the ripe proglottid 

 is transferred from the chyle to clean sea-water will, I think, con- 

 vince any one that the same process occurs when a ripe proglottid 

 of Crossobothrium passes in the normal course of its existence 

 out of the shark's cloaca into the water of the ocean. We may 

 conclude I think that such a proglottid, upon coming into contact 

 with the sea-water outside, goes through muscular contractions 

 similar to those observed in the laboratory and lays its eggs free 

 in the open ocean, and that these pelagic eggs are thus widely 



