STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAX. Ig5 



asymmetry presents itself in some internal organs, as in the different lengths of the 

 two branches of the intestine, (2) In all the species of Mtcrocoti/le what Lorenz 

 calls " Penis " is distinctly present ^^ as also the genital cloaca, and his observa- 

 tion as to the separate opening of the male and female ducts is, as Par on a and 

 Perugia have pointed out, erroneous. (3) In the species of J.rine which I have 

 studied, and which are described below, the vagina is situated, as in Microcotyle, on the 

 dorsal median line. (4) I have observed some specimens of A.ciiie hcterocerca dis- 

 charge, while kept in sea-water in a watch-glass, a large number of eggs from the 

 uterus, which was afterwards found to be much enlarged in consequence. (5) In all 

 the three species of Axine I have studied, two series of suckers are distinctly present, 

 although one of the series is much reduced in number. Thus we find no absolute 

 difference between the two genera, the difference lying only in the degree in which 

 the asymmetry is manifested in each. Still the general form of the two genera 

 presents quite a perceptible difference, so that wo may keep them distinct for con- 

 venience' sake. A sharp distinction between two such nearly allied genera can not 

 be expected. 



In view of the facts above summarised, the diagnoses given by the preceding 

 writers are no longer quite satisfactory ; I therefore venture to modify them as 

 follows : ; 



Body elongated, mo s t ] y s y m metrical, with the a n - 



terior end rounded and the posterior end usually pointed. 



With a pair of suckers in the mouth-cavity. The caudal 



disc, which is in most species separated from the hody 



proper by lateral constrictions, usually bears a large 



number of minute suckers. Genital cloaca present ; 



genital opening on the ventral median line ; vaginal 



opening single, situated in tlie median line on the dorsal 



side. No chitinous hooks at the posterior end of the 



body. 



1). Cf. Paronr. and Perugia— Res lig-nsticae, XIV. p. 8. 



