STUDIES ON THE ECTOPAEASITIC TKEMATODES OF JAPAN. 83 



Doubt has been expressed by some writers whether the meshes 

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

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

 running within them. Poirier'^, for instance, on the ground of his 

 observations on Distomum. decides for the former view, and seems to 

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

 I believe, clear from my descriptions above that considerable v.ariations 

 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-organs on the surface of the body I have not 

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

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



9, The Eeprodiictive System. 



Since the general view of the reproductive organs can easily be 

 obtained from the plates accompanying this paper, I shall at once 

 proceed to the description of the constituent parts. 



(a) The Male Organs. 



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 Diclidophora sessilis (PI. X, fig. 5), 

 Tristomum ovale (PL XXIII, fig. 1), and the genus Octocotijle (PL IX, 

 figs. 1 & 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 I'histoire uiturelle des Trematodes. Arch. d. Zool. exper. et 

 generale. T. Ill, 1885. p. 603. 



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

 di Naturalisti in Sapoli. Ser. 1, vol. 5, 1891, fasc. 2. 



