nature of the disc and he separates a new genus Amphibdelloides which 

 differs by the presence of the connecting plate in the disc which does not 

 form any lobes in contrast to the genus which in his opinion is deprived of 

 a connecting plate and has a disc with numerous "lobes. " During the 

 verification of considerable material it became clear that Ainphibdella 

 always has one connecting plate. Among younger samples it really is 

 expressed nnore distinctly, whereas among older individuals it is relatively p. 392 

 poorly noticeable, especially in stained whole mounts. This plate is 

 exceedingly thin and tender and apparently its relative growth is very weak 

 so that in large specimens it has a rudimentary nature, so to speak. As 

 regards the presence of the second plate which was indicated by Parona 

 and Perugia, they mistook for it the transversal muscular band which 



connects the upper ends of the ventral pair of the middle hooks. This band 

 is clearly apparent in a number of preparations and perhaps is really more 

 easily noticeable among young individuals. Consequently, the character, 

 presence or absence of the connecting plate which is basic for the division 

 of Amphibdella into 2 genera by Price is not valid. Just as unimportant is 

 the second sign--the formation of "lobes" on the disc. The so-called 

 "lobes" actually are contractile portions of the body of the disc in which 

 the hooks are located. Such outgrowths are formed on the bodies of 

 practically all monogenetic trematodes during ■ftie attachment of the latter 

 to the gills of the host, and appear, or disappear within strictly determined 

 areas of the disc in connection with the constant distribution of edge hooks. 

 One can note at the same time that during the preservation of younger indi- 

 viduals these outgro'wths have already been removed by the worm before its 

 death; whereas among the older ones they are affixed partially or fully in 

 the elongated state. It is difficult to say what happens here but the slowing 

 of the reaction to the fixing fluid is clearly shown in the individuals. As a 

 matter of fact, this concerns not only the attaching disc but also the cephalic 

 outgrowths as well as the general contraction of the body (it is understood 

 during equal conditions of physiological "freshness" of the material). We 

 also seem to see the same relation in Amphibdella. The younger individuals 

 are more often fixed with retracted hooks and correspondingly the disc has 

 a contracted shape (Fig. 285)', whereas larger fixed specimens have more 

 or less elongated shapes and the hooks are protruded further outside to- 

 gether with the adjacent sections of the disc itself (Fig. 285, B). However, 

 the relative position of the hooks in both individuals is completely the same. 

 The location of the "lobes" on the drawings of Ruszkowski and on the p. 393 



figures of A. flavolineata in Price (Price, 1937b, Fig. 1) is approximately 

 correct. 



To the present time the internal structure of the representatives 

 of the genus Amphibdella has also not been described very accurately. Thus 

 Ruszkowski and subsequent authors represent the widening part of the 

 s eminal duct as a testis (=vesicula seminalis externa) whereas actually the 

 testis lies behind the ovary and at any rate begins not higher than the middle 

 of the flask-shaped part of the ovary. The fact that the testis is poorly 



469 



