THE SCOLEX POLYMORPHUS $45 
ment. Seven small specimens of P. triloculatum were collected, 
but in this case it was evident that the valve contained a much 
smaller number of these than the previous one. My notes 
taken at the time state that no more were seen in addition to those 
actually collected, although there may have been some toward 
the anterior end where the villi are longest. Specimens Nos. 5, 
6 and 7 all present evidence against the effectiveness of the ver- 
mifuge. In 6 and 7 the numbers of surviving cestodes is so 
great that no certain effect from the drug is indicated. There 
is perhaps some significance in the fact that here, as in some 
other cases where the worms are found surviving the effects 
of the oil, the proportion of young to adult specimens is 
somewhat increased. This may indicate that the drug is more 
effective with the large worms which have long bodies extending 
among the folds of the valve than with very young ones which 
may often be almost buried among the villi and so escape the 
full effects of the drug. In this table there are recorded from 
specimens 4, 5, 6, 7, 8 and 9 a total of 48 surviving Crossobothria. 
Of these only 9 are beyond the period of segmentation into 
proglottids and from what we know of the proportions in which 
the young and old are commonly found it would seem that the 
drug has destroyed more adult than young worms. This con- 
clusion is of course based upon my belief that these young Crosso- 
bothria have not come from the introduced 8S. polymorphus. 
In sharks Nos. 8 and 9 the same condition was found as in No. 
3, namely, so many specimens of small P. triloculatum that the 
counting them was an impossible task. Later when I examined 
very carefully the preserved specimens I[ found that the Phoreio- 
bothria from any one shark were of uniform size, but that when 
those from different sharks were compared there was some differ- 
ence in the size attained. For instance those from specimen 9 are 
almost twice the size of the ones from specimen 3. This differ- 
ence in size is noticeable only in the body portion of the larvae, 
the scolices being of very uniform size. 
The presence of the C. laciniatum and a few C. angustum, 
although there are more young specimens among them than one 
would expect to find in sharks taken at random, does not seem 
