GYEODACTYLTD.^*]. 47 



lets or not, remarking in the first instance their position, form, 

 distribution, and so forth. 



d. ^^ The integument is sometimes wrinkled transversely, at 

 other times appearing to be smooth. 



e. " The muscular apparatus is, in certain cases, very strongly 

 developed. In the majority of instances special muscles are inserted 

 into the handles of the hooks, and they are also very frequently 

 directed into the transverse muscles of the skin. In Gyrodactylus 

 crassiusculus, we find a jjrotrusor penis and retractor palparum 

 medius. 



f. "Except in the case of G. elecjans, four so-called eye spots 

 are observed at the anterior extremity of all Gyrodactyli. As 

 Siebold says, they answer the purpose of light-refracting organs. 

 The palpi — which in G. crassiusculus are seen to contain muscular 

 bundles — appear to be retractile touch-organs, extending more or 

 less prominently forward. 



g. " Observations in regard to the alimentary canal are at present 

 incomplete, for only in the case of Gyrodactylus cochlea did I find a 

 single gullet demonstrable. This was furnished with epithelium, 

 being tinged either yellow or brownish yellow. It passed from 

 before backwards, and was probably furnished with an anus, 

 whilst, in all other instances, its passage could not be traced. The 

 reason of this arises from the transparency of the intestinal con- 

 tents, and fi-om the internal blending of the wall of the canals with 

 the parenchymatous substance. The other organs also hinder our 

 observation. 



li. " In three species of Gyrodactylus, namely, in G. cochlea^ 

 G. crassiusculus, and G. tenuis, the generative organs are thus 

 disposed : — The vitelline organ is characterised by its botryoidal 

 structure, and its round secretion-cells containing granular matter. 

 These organs are so completely enveloped by a limiting mem- 

 brane that there is no direct connexion between them and the oral 

 sucker. The excretory duct lies in front of the ovary. In all the 

 Gyrodactyli, where, generally speaking, one egg with its yellow 



