132 W. C. CURTIS. 



When carefully examined the ripe proglottids at the posterior 

 end of a strobila (Fig. 5) or the mature motile proglottids found 

 free in the chyle show a breast-like protuberance upon that face 

 on which the uterus opens. The resemblance of this to a breast 

 is heightened by the existence of a nipple-like prominence at the 

 summit, as is shown in the side view given in Fig. 5. The general 

 protuberance is caused by the distension of the uterus, though it 

 sometimes seems to be enhanced by a concavity on the opposite 

 face of the segment as the dotted line of the figure indicates. 

 Motile proglottids when in this ripe condition show, if examined 

 in the chyle, the ordinary writhings and indefinite locomotor 

 movements noted above. If, however, a number of these ripe 

 and full proglottids are transferred from the chyle into clean sea- 



FlG. 5. Side view of a ripe proglottid. 



water the egg-laying will presently be observed. In making 

 observations on this process I was accustomed to select carefully 

 ten or a dozen proglottids which seemed fully ripe and transfer 

 them all together into a dish of clean sea-water. When this was 

 done it was found that about eight out of ten thus selected laid 

 their eggs in three or four minutes. Any of those remaining 

 might lay after a little longer period or not at all. A similar 

 reaction of whole chains of proglottids is recorded by Schauinsland 

 (Jena, Zeitsch. 1886), for Botlirioccplialits latns, Trianophorus iiodu- 

 losns and Lignla simplissima. 



When proglottids of Crossobothrium are taken at random and 

 thus placed in sea-water only a small proportion, no more than 

 one fourth or one fifth, will ever lay their eggs. When the small 

 proglottids which have only a few eggs in the uterus are thus 

 taken no egg-laying follows in any case. 



That the proglottids as found in the spiral-valve at any one time 

 are not all of same maturity is thus clearly shown and I think we 

 are justified in the conclusion that these immature proglottids 

 tend to remain in the spiral-valve until they become fully ripe 



