STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAN. 9 



granules are also observable. In all the other species, the subcuticle 

 shows only granules, which are, however, more numerous in some 

 than in other sjiecies. For instance, in Microcolijh', Ajcine, Monocottjle, 

 Dididoplioni. and Hexacotijlc the granules are comparatively sparse, 

 while in Trisfonnnn thev are very numerous and exceedinoly fine in 

 certain regions, ('.(j. on the ^•entral side of the anterior suckers. 



Inward to the subcuticle comes the Jun^auent vuniihiriNt\ In cross- 

 sections it is very deeply stained, and very distinctly separable from 

 the subcuticle Ijut somewhat less so from the subjacent mesenchyma. 

 Its thickness can not be measured with any accuracy, but it is always 

 thicker than the cuticle. Ilallez'^ has shown with regard to plana- 

 rians, that the basement membrane is of the same nature as the dense 

 layer of connective tissue tli:it surrounds the internal organs. Gene- 

 tically therefore it belongs to the mesenchvma rather than to the 

 investing membrane, and it is only in accordance with custom that 

 I have described it as forming one of its layers. 



In Tn'stominu sinvatum and Trist, ovale there are numerous 

 papillae on the surface of the body. These are of two kinds. Those 

 of one kind are mostly perceivable with the naked eye. In Trist, 

 siminhnii tliey are confined to the dorsal surface of the body, and 

 measure on the average about 0.028 mm. in height, the extremes 

 being 0.014 mm. and 0.041 mm. ; the larger ones appearing to the 

 naked eye as granulations. In Trist, ovale, on the other hand, they 

 are confined to the ventral side where they are very numerous, and 

 :n*e much larger than in Trist, siiiutitum, measuring on the average 

 about O.OS mm. in height, the extremes being O.Ooi mm. and 0.122 

 mm. The papillae of the other kind are all micr(jscopic and are far 

 less numerous than those c^f the first kind. In 'Trist, ovale they are 



1). Ilallez— Euibryogvnie des Dendrocoeles d'oau douce, 1SS7. p. 78. 



