STUDIES ON THE ECTOPAEASITIC TREMATODES OF JAPAN. H 



nature. These views may be divided into two classes, viz., that which 

 resrards the investinff membrane as a true cuticle, and that which 

 regards it as the transformed product of the originally cellular 

 epidermis. Among the most recent writers on ectoparasitic Tre- 

 matodes, Br an des. represents the first view and Braun the secoiid.'^ 

 According to the former writer^^ the investing membrane is to be 

 regarded as a true cuticle and as the secretion product of numerous 

 unicellular glands scattered in groups in the cortical portion of the 

 mesenchyma (Ectoparenchym), the presence of which he claims to have 

 demonstrated in all the forms studied by him for the purpose. In 

 opposition to this view, Braun'^ brings forward the fact that in Mom- 

 stomum mutahile there are disseminated in the investing membrane 

 (" Hautschicht ") numerous oval nuclei with sharp outline and stain- 

 ing weakly with picro-carmin. In absence of any direct embryolog- 

 ical proof it is of course useless to dogmatise on either side. But, even 

 laying aside the fact observed by Schwarze^^ that the investing 

 membrane of Cercaria is a transformed epidermis as not quite conclu- 

 sive with respect to that of the adult worm, the positive facts^^ 

 at present known, when taken together seem to me to be strongly in 

 favour of the view upheld by Braun. For instance, the observa- 

 tion of Zeller^^ on Polystomum, that in it the epidermal cells are not 

 cast off but have their nuclei merely shrivelled up, strongly points to 



1). As stated in a previons note Monticelli is of the same opinion. 



2). Brandes — I. t. 



3). Braun — XJeber einige wenig bekannte resp. nene Treinatoden. Verhandl. d. deutsoli. 

 zool. Gesellsch., 1892. p. 51. 



4). Schwarze — Die postembryon. Entwickl. d. Trematoden. Zeitsch. f. wiss. Zoolog., Bd. 

 42, 1886. p. 49. 



5). It is perhaps hardly necessary to remark here that the " matrix cells '' of Wierzejski 

 are in reality the nuclei of the mesenchyma. Gf. Wierzejski in Zeitsch. f. wiss. Zoolog., Bd. 29, 

 1877. p. 552. 



6). Zeller— Weiterer Beitrag z. Kenntniss d. Polystomen. Zeitsch. f. wiss. Zoolog., Bd. 27 

 1876. p. 262. 



