visible on whole mounts is explained by its relatively small dianneter. As 

 a rule, the testis is rather long and contains an insignificant number of 

 ripe spermatozoids, being basically filled with their earlier stages. In 

 connection with this, it is apparent that there is strong development of the 

 vesicula seminalis externa. The works indicated have inaccuracies in the 

 expression and description of vitellaria, cephalic glands, etc. on which 

 we are unable to dwell now. 



Thus, so far only one genus, 

 Amphibdella-- synonymous to which 

 is the genus Amphibdelloides- -should 

 be considered as having the right to 

 exist and be considered in the compo- 

 sition of the family. The independence 

 of the family was first indicated by 

 Carus (Carus, 1885), however^ clearly 

 erroneously because he ascribed this 

 family to the order Trennatoda, sub- 

 order Digenea, having placed it to- 

 gether with the family of Amphillinidae 

 in front of Monostomidae. After his 

 work, no one paid any attention to this 

 separation of Amphibdella into a 

 separate family and ascribed this genus 

 quite correctly for that time to the 

 family of Gyrodactylidae, and later 

 after the separation of the family of 

 Dactylogyridae--to the latter. Never- 

 theless, at the present time there is 

 basis for the re -establishment of the 

 independence of the family, but 

 for other reasons. As we have already 

 indicated, the genus Amphibdella must 

 be excluded from the suborder Dactylo- 

 gyrinea and transferred to Tetraonchidea 



Cm: 







Fig. 284. Annphibdella torpedinis 

 Chatin, adult worms from the gills 

 of Torpedo marmorata Risso from 

 the Basin of Arcachon {Atlantic 

 Ocean). 



(sic). Within the limits of the last suborder this genus stands closest to the 

 family Tetraonchidae. However, Amphibdella differs by a number of charac- 

 teristics which do not permit it to be included in the present family and 

 which force us to recognize the necessity of separating it into a separate family. 

 The presence of the two -branched intestine in contrast to the one -branched intestine of 

 Tetraonchidae should be considered as the first and most important characteristic. Taking 

 into consideration the rarity among Monogenoidea of the one-branched intestine indicated 

 above (see page 47) and the Indubitable primitiveness of this characteristic, one should 

 not unite the species which have one- and two-branched intestines^ into one family. 

 Further, even though the absence of the eyes is undoubtedly a 



470 



