FORMATION OF PROGLOTTIDS IN CROSSOBOTHRIUM. 215 



the primary strobilla would be considerable unless one of the old 

 anterior proglottids still remained and I have not felt that the 

 prospect of finding such stages justified my delaying the com- 

 pletion of this paper until I had another opportunity to examine 

 a large amount of fresh material in search of them. This seg- 

 mentation of the neck region is either the beginning of a new 

 strobilla which to distinguish from the earlier we might call 

 the secondary strobilla, or it is simply an abortive attempt in the 

 old age of the individual and comes to naught. From what we 

 know of the longevity and continued production of proglottids in 

 a few other cestodes, Braun, p. 1604, I think the presumption is 

 distinctly in favor of the former view, viz., that the segmentation 

 which I have observed beginning in the neck region is the first 

 step in the formation of a new strobilla. Though it would be 

 almost impossible to demonstrate the formation of other strobillae 

 from new neck regions after the secondary one has in turn become 

 exhausted, we may, I think, consider such a process as not at all 

 unlikely. Hence, we have the suggestion that what may be 

 called primary, secondary and tertiary, etc., strobillae are suc- 

 cessfully headed off by a single individual scolex. 



(W) An Exceptional Condition, Perhaps to be Explained as Re- 

 generation a f ter Chance Mutilation. Two specimens have come 

 under my observation which apparently do not find any place in 

 the above scheme of development. One of these is shown in 

 Fig. 19 of PI. VI. In this we have a body with a definite zone 

 region and the anterior and posterior segments which character- 

 ize a worm developing the primary strobilla. In contradiction to 

 these features, we find a well-developed neck region. The size 

 of the bothria gives no trustworthy evidence of the age in these 

 specimens. I think these two exceptions may be explained as 

 cases of regeneration after a chance mutilation occurring under 

 natural conditions. 



It will be noted if Fig. 19, PI. VI., is compared with Fig. 12 

 of PI. V., that the number and development of the anterior pro- 

 glottids is relatively much greater in Fig. 19 than we find in the 

 normal development of the primary strobilla. If such a speci- 

 men as Fig. ii or Fig. 12, PI. V., had been cut in two some- 

 where near the forward region of the posterior proglottids and 



