filO W. S. NICKERSON, 



Position render it probable that they are spine gküds (Stacheldrüsen) 

 such as occur in larval stages of many Distomidae. I have not been 

 able to detect spines in those studied but their absence finds a suf- 

 ficient explanation perhaps in the extreme youth of the embryos. If 

 my interpretation of these cells is correct their presence gives reason 

 for believing that Cotylogaster is like Stichocotyle in having two hosts 

 and that it is makes its way into the first of these by the use of 

 spines. I have already suggested it as probable that a similar method 

 of infection of the primary hosts occurs in the case of Stichocotyle 

 (NiCKERSON '95, p. 478). The conditions in the embryo of Cotylo- 

 gaster not only increases the probability that that Suggestion was cor- 

 rect but also suggests the further inference that the Aspidopothrids 

 generally live in two successive hosts, the intermediate host being known 

 only for Stichocotyle. 



In the middle portion of the body of the embryo ventral to the 

 intestine is a mass of granulär tissue containing large nuclei with 

 prominent Single nucleoli. It is probably the rudiment of the future 

 sexual Organs. Mitotic figures are occasionally seen in these nuclei 

 one such being shown in Fig. 18. 



The only other Aspidobothrid embryo available for comparison 

 with that of C. occidentalis is that of Aspidogaster described by 

 VoELTZKOw ('88). A number of points of resemblance between the 

 two have been alluded to. Their most prominent dift'erences are 

 1) the absence in C. occidentalis of the rudimentary tail which Voeltz- 

 Kow described in Aspidogaster] 2) the absence in C. occidentalis of 

 a distinct oral sucker as described and figured for Aspidogaster and 

 3) the presence of cilia in tufts upon the body of C. occidentalis which 

 are absent in Aspidogaster. 



The latter ditference necessitates dropping one of the family cha- 

 racteristics as stated by Braun, viz. the absence of cilia upon the 

 developing embryo. 



The systematic position of the new worm remains to be con- 

 sidered. I give below (p. 611) in tabular form a Statement of the 

 Chief differeuces between it and Cotylogaster michaelis as described by 



MONTICELLI. 



Most of the differences mentioned are undoubtedly of only specific 

 value. A few of the others may perhaps be regarded as of sufficient 

 importance to Warrant the establishraent of a new genus for the form 

 exhibiting them. Such are the differences in the condition of the 



