middle "parenthesis". The precise structure of these seams is not clear 

 because we did not have sections of suckers of Chimaericola,' however, 

 judging by analogy from Diclybothrium these seams represent the place 

 where the membranes of the right and left halves of each valve join, be- 

 cause the subcuticular membranes of the disc is not a single whole but 

 consists apparently of two separate parts representing sheaths so to 

 speak, covering each half of both valves on all sides. This is not alto- 

 gether accurate and it is possible that there are not two sheaves but even 

 four. It is clear from the above-mentioned that even in such a primitive 

 form as Chimaericola the clamp is a very complex formation differing 

 considerably not only in its function but also in its peculiarities of morpho- 

 logical structure from the suckers peculiar to Polyonchoinea. 



Very important is the question concerning the chitinous 

 "parentheses" of the clamp, their structure and origin. If this question 

 has already been discussed in general traits (see page 32), on the other 

 hand, for Chimaericolidae it represents particular but nevertheless 



important interests. During the examination of all three parentheses , the 

 first thing that jumps to the eyes is the coinpletely different "facteur'' 

 ( make-up or structure, nobis) of these formations. Thus, the middle 

 "parenthesis" is homogeneous and produces the impression of being very 

 dense and compact, whereas both lateral parentheses have a different 

 structure, but with greater numbers of slit-shaped depressions located 

 along their interior surfaces and they appear to be more frail in spite of 

 their considerable sizes, It is noteworthy that in a nurnber of cases in 

 glycerin -jelly preparations which we have of the clamps it is clear that 

 they have a yellow color, whereas the middle "parenthesis" is absolutely 

 white. As regards the middle "parentheses" its shape in the extreme 

 resembles the one of the hooks of the clamp of Diclybothriidae. Thus, 

 even during careful examination of the anterior end of this "parenthesis," 

 which is very sharpened in comparison to the rounded and thickened 

 posterior end, one can often notice a more or less distinctly expressed 

 hook-shaped curvature corresponding to the edge or point of the hook of 

 Diclybothriidae. This is seen especially distinctly on preparations of 

 younger samples of Ch. leptogaster Leuckart and on the only individual 

 of the new species. The ends of both lateral parentheses have a completely 

 different character; as a rule they gradually narrow and terminate in a p, 414 



more or less rounded form, and at the same time each is alike at both 

 ends. Hence, one can consider, it seems to us with a great degree of 

 probability, that the middle "parenthesis" and the edge ones have a 

 different origin in the first place, and in the second place that the middle 

 parentheses of the clamps of Chimaericolidae are homologous to hooks 

 of the suckers of Diclybothriidae and consequently represent strongly 

 altered edge hooks of monogenetic trematodes. Unfortunately, until 

 additional material on the development of Chimaericolidae is obtained, the 

 last conclusion, probable as it may be, nevertheless remains conjectural. 

 However, one can say that the attaching clamp of Chimaericolidea and 

 Diclybothriidea are the most primitive in the group Oligonchoinea. In 



495 



