2l6 WIXTERTON C. CURTIS. 



by this loss of a considerable portion of the young strobilla, the 

 part having the scolex had been stimulated to form a neck for 

 the production of more segments, we should have such a condi- 

 tion as Fig. 19 shows. It is commonly assumed in the theories 

 regarding the nature of the cestode body that the Cestoda have 

 great powers of regeneration. For example, Lang ('88) used 

 this supposed capacity for regeneration as the starting point in his 

 explanation of how the strobillization was first introduced into 

 cestode phylogeny. We have, however, little in the way of 

 direct evidence either from observation of specimens regenerating 

 under natural conditions or from accounts of their regeneration 

 under experimental control. The difficulties of technique have 

 so far as I know prevented any experimental confirmation of this 

 supposed power of regeneration. Still the assumption seems 

 reasonable and the difficulties could doubtless be overcome if it 

 seemed worth while to determine what regenerative powers the 

 Cestoda do actually possess. In the case of C. laciniatum one 

 should be able to test the explanation I have just given for these 

 exceptional cases by the mutilation of young specimens in the 

 way indicated. If one could overcome the difficulties and keep 

 the worms alive by introducing them into another shark or other- 

 wise, I think some very interesting data might be obtained by the 

 mutilation of strobillae in different stages and a study of the 

 regeneration if such a process occurs. 



(e) Histology of the Non-Segmented Zone in Voting Worms and 

 of the Neck Region in Older Specimens. I have examined 

 sections of this region which is the place where differentiation 

 appears to be most active hoping to find some characteristic 

 features by which its histology might be distinguished from that 

 of the ordinary proglottid, but with the material available have 

 not been able to recognize any such distinguishing features. If 

 nuclear division is in progress it must be amitotic such as Child 

 ('04) has recently described for Moniezia, for the material I have 

 would show clearly the existence of mitotic figures. I have 

 endeavored by staining after the method followed by Child to 

 determine the presence or absence of such division but the fixation 

 is not quite good enough for this point. This histology seems 

 to be much the same as that of the formed proglottid save that 



