as a basis for this serve: 1) the absence of supplementary discs 

 ("squannodisk" of the authors) or cuticular plates in the attaching disc; 

 2) the presence of separate clusters of needle-shaped hooks which are 

 formed in the parenchyma of the attaching disc and the points of which 

 extend beyond its surface, and; 3) the presence of a number of spear- 

 shaped hooks in the posterior parts of the body ("stem" of the disc). The 

 authors write about this: "The above-mentioned structures just as the 

 thorns in the disc are not cuticular in origin but are from the parenchyma and, 

 in this connection .resemble the middle hooks, the edge hooks and the 

 structures of the copulatory complex. " 



As we have often indicated earlier, in spite of the fact that 

 the chitinous elements of the disc are incepted in the parenchyma, they 

 are undoubtedly of cuticular origin, and thus the opinion of Monaco, Wood 

 and Mizelle in this connection is erroneous. Erroneous also is their juxta- 

 position of the arnnature of the supplementary disc with the spear-shaped 

 thorns lying on the same disc, as well as above it on the "stem" of the 

 body. As has been mentioned before, these are homologous formations. 

 It is obvious that for all the exannined structures, even though they be of 

 cuticular origin, their inception can only take place at the expense of the 

 cells lying under the cuticule (cells of the subcuticular epithelium? -- 

 compare however, page 41 ), Taking what has been said into consideration, 

 the first and the third instances which distinguish Rhamnocercinae from 

 Diplectaninae according to Monaco, Wood and Mizelle are interconnected 

 and so to speak both subfamilies differ only by one characteristic- -by the 

 change from one type of supplementary armature to another which is 

 homologous to the first. As regards the internal organization, so far we 

 don't know of any morphological differences bet'ween the two groups. 

 Nevertheless we are inclined to accept the point of view of Monaco, Wood 

 and Mizelle and to recognize the justification of isolation of the subfamily 

 by taking into consideration the sufficiently sharp break between the 

 structure of the supplementary armature of both groups and particularly 

 taking into consideration the appearance of the thorns on the disc (the 

 second characteristic of the authors) which is, as we have already noted, 

 a secondary phenomenon and new for the group. 



The position of the genus Lepidotrema in the system of the 

 family is not clear. Characteristic for it, in addition to the special 

 structure of the secondary attaching armature, is the bifurcation of the 

 lateral parts of the connecting apparatus of the middle hooks --among 

 representatives of this genus there are 5 connecting plates and not 3 as 

 among typical genera of both subfamilies. Apparently this structure is 

 secondary. A basis for this supposition is the fact that among the 

 majority of the lowest Monogenoidea an increase in number of connecting 

 plates takes place, whereas their initial number corresponds to the 

 number of pairs of middle hooks. The presence of 2 plates can be con- 

 sidered as primary for Diplectanidae and only afterwards did the bifur- 



424 



