176 S. GOTO. 



now so often used by German and other continental writers, and 

 also by some English-writing authors, that I believe myself justified 

 in adopting it too^— and in the sense in which it has been used 

 by P. J. V. Beneden'^ and just now defined in this paragraph. 



In conclusion I wish to make a short remark on the terms 

 " vagina " and " Laurer's canal " as applied to the Monogenea. The 

 former possesses, etymologically speaking, only a physiological signi- 

 fication, and it is very unfortunate that Monticelli has attached to 

 it a morphological meaning, and has called the Laurer's canal vagina, 

 although, according to his own opinion, not this canal but the 

 " ovidotto esterno " functions as such ; so that if we should adopt 

 consistently Monticelli's terminology we should be led to some 

 such awkward expressions as " the vagina of the endoparasitic Tre- 

 matodes.is not a true vagina but the ' ovidotto esterno.' " " Laurer's 

 canal " now so familiar to helminthologists ought, in my opinion, 

 to be retained, as its homology is still under discussion. It is, on 

 the other hand, not advisable to apply the name to the vagina of 

 the Monogenea, as has been done by some writers. For, in the first 

 place, we have for this group such a good name as " vagina," and in 

 the second place — and this is a very serious objection — the homology 

 of the two canals is far from being yet made out. It is therefore 

 to be hoped in the cause of science that we shall use non-commital 

 terms, and simply speak of the " vagina" of the Monogenea, and the 

 " Laurer's canal " of the Digenea. 



B. Biological Notes. 



Habitat — The particular habitat of each species will be stated 

 in the systematic part of this paper ; but some general facts must be 

 noted down here. By far the greater number of ectoparasitic Tre- 



1). p. J. V. Beneden— i. c. p. 15. 



