STUDIES OX THE ECTOPARASITIC TKEMATODES OF JAPAN. <;^3 



Doubt has been expressed by some writers wliether the iiieslies 

 of the nerves represent themselves the cross-sections of nervous fibres, 

 or whether they are tbrmed by the connective tissue with the fibres 

 runninsf within them. L*oirier'\ for instance, on the £>Tound of his 

 observations on Di^itomum decides for tlie former view, and seems to 

 believe the same to l)e the case also in the Turbellaria ; but it will be, 

 I believe, clear from my descriptions above that considerable variations 

 must be allowed for in this respect, and that the results obtained from a 

 single species or genus can not be applied in toto to others. 



About the sense-oro-ans on the surface of the bodv I have not 

 been able to make any minute observation, and will oidy refer the 

 reader to the interesting paper of Monticelli"^ already mentioned. 



9. The Beprodiictice Sijsteiu. 



Since the general view of the reproductive organs can easily be 

 obtained from the ])lates accompanying this [»a per, I shall at once 

 proceed to the description of the constituent parts. 



(a) The Male Onjan><. 



Testes — In all the species described in this paper there are more 

 than one testis, and these are as a whole situated in the posterior 

 part of the body behind the ovary. The only exceptions in this 

 respect that T have observed are in Diclidophom ses.silis (PL X, fig. 5), 

 Tristonium ovale (IM. XXIII, fig. 1), and the genus Oeloeotijle (PI. IX, 

 figs. 1 et 7). In the first of the species just mentioned, there are 

 numerous testes, and these are situated not only in the posterior part 



1). Poirier — Contribution a l'histoire naturelle des Trematodes. Arch. d. Zool. expér. et 

 générale. T. Ill, 1885. p. 603. 



2). Monticelli — Di alcuni organi di tatto nei Tristomidi. Estratto dal Boll, della Soc. 

 di Xaturalisti in Xapoli. Ser. 1, vol. 5, 1891, fasc. 2. 



