144 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 39. 



with perhaps a few lobes filled with eggs or containing only a few eggs. 

 This suggests that we have here a condition similar to that in Callio- 

 hotlirium and aUied genera, where the uterus ruptures on the dorsal 

 or ventral side. A further suggestion of this is found in some sec- 

 tions where a uterine lobe extends past the limiting musculature of 

 the inner parenchyma and reaches clear to the cuticula. The eggs 

 in this lobe are not yet completely developed. Eggs were observed 

 to escape from one end of a loose proglottid as it crept about \nth a 

 leech-hke movement, but tliis method of releasing eggs is common 

 enough in other Tsenia forms in which a similar large number of 

 fresh gravid proglottids do not show a uterus nearly or quite empty. 



The eggs are ovoid in shape, the long diameter varying from 29 to 

 37 p. and the short diameter from 27 to 33 fi, the average dimensions 

 being 35 by 31 /i. The shell is about 4 /« tliick. 



In some cases the genital canals pass to the genital pore dorsad of 

 the main nerve and the main or ventral excretory canal and ventrad 

 of the dorsal excretory canal. Where this happens the main nerve 

 trunk and the ventral excretory canal lie side by side in almost the 

 same plane. In other cases the genital canals pass between the main 

 nerve trunk and the ventral excretory canal, in which case the nerve 

 trunk rises to pass dorsad of the canals at that point. 



The excretory system is notable for the great development of the 

 transverse canal. In the gravid proglottids this occupies a position 

 between two proglottids instead of being in the posterior part of the 

 anterior proglottid. Tliis condition is indicated in figure 8, showing 

 a toto mount and sho%vn in sagittal section in figure 9. The valve in 

 the ventral canal, located at the posterior end of the proglottid is so 

 well developed that in toto mounts of gravid proglottids there appears 

 to be no connection between the transverse canal and the ventral 

 canal of the same proglottid. This is indicated in figure 8. Where 

 the two canals join the transverse canal is dilated to form a sort of 

 reservoir. The valve-guarded aperture of the transverse canal open- 

 ing into this from the anterior end has a diameter usually only a third 

 or fourth as great as that of the unguarded aperture of the lateral 

 canal of the following proglottid. The lateral canal, where it passes 

 back from the transverse canal, in gravid proglottids turns toward 

 the median part of the proglottid, forming a sharp angle ^^•ith the 

 transverse canal. (See fig. 8.) 



The worm has a well-developed layer of transverse muscles and 

 several discontinuous and ill-defined layers of longitudinal muscles. 



Calcareous corpuscles are abundant and of variable shape. Some 

 of the larger measure about 20 /z in the long diameter. 



In an attempt to determine the life-history, proglottids showing 

 the hexacanth embryo were fed at various times to six rabbits, two 



