STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAX. 183 



pliasis, on the usefulness for systematic purposes of the examination 

 of the hooks which are often present near the posterior end of the 

 body. Drawings of them made from glycerine-gelatine preparations 

 as mentioned at the beginning of the present paper would be of in- 

 valuable service in the identification of species. Indeed, different 

 species of the same genus can be distinguished and identified with a 

 good degree of certainty by proper examination of these hooks alone. 

 AVhen one has a new species before him and yet has not time enough 

 to make a sufficiently minute study of it, he would do well to add 

 to its more prominent characteristics a sketch of the hooks from a 

 glycerine-gelatine preparation, care being taken to bring them to 

 such a position as to enable him to get a good view of the characteris- 

 tic form — a job which can usually be effected with ease by repeatedly 

 melting the imbedding medium and giving proper shifts and pressure 

 to the cover-fflass. 



o 



I. MiCROCOTYLE, P. J. v. Beneden et Hesse. 



Tins genus was first erected in 1863 by P. J. van Beneden and Hesse with 

 the following diagnosis ') : " Une partie du corps est separee en arriere par uu 

 etranglement et porte, das deux cotes du corps, un tres-grand nombre de petites 

 ventouses a crochets. Les ceufs sont munis d'un filament aux deux poles.'' These 

 writers have described five species, viz., M. labracis from the gill of Labiax hijnis, 

 M. canthan from the gill of Cantliariis griseus, M. donavani from the gill of Labnis 

 donavani, M. enjthnai from the gill o( Pagellus erythrinus, and M. ehrysophrii from the 

 gill of Chrysophris vidyaris. 



In 1878 Vogt^^describedanew species, M.mvgiUs, from the gill of il/H^fiZ ce/j/iaZus. 

 According to this writer this genus should be united with A.dne, since "die 

 innere Organisation ist durchaus dieselbe, nur ist bei Axine orpliii . . . der Vorder- 

 theil des Korpers weit melir in die Liinge gezogen und sohmal, wtlhrend zugleich das 



1). P. J. T. Beneden et Hesse — Recherohes sur les Bdellodes et les Trematodes marins. 

 p. 112. 



2). Vogt— TJeber die Fortpflanzungsorgane einig, ectopar. marin. Trematoden. Zeit- 

 sohr, f. wiss. Zoolog., Bd. 30, Suppl., 1878. 



