Japanese Tricladitla Maricola. 7 



drical cells which vaiy in height not only in different species 

 but also in different body parts of the same individual, largely 

 depending upon the condition of expansion or contraction of the 

 worm. It is generally thickest on the dorsal surface, and as it 

 passes over to the ventral surface, gradually becomes thinner as far 

 as the middle line, it measuring in Pr.. lactea 12 ^ dorsally, 8 t^ 

 ventrally ; in St. trigonocephala 8 /^ dorsally, 5 /^ ventrally, and 

 in Ect. limnli 9 f^ dorsally, 7 <" ventrally. 



The protoplasm of the cell is generally fibrillated, as observed 

 by a number of investigators. The courses of the fibrillae are 

 more or less irregular, though in a general way perpendicular to 

 the surface. Frequently, but not always, they form a network, in 

 which the spherical or ovoid nucleus, as a rule, lies near the base 

 or the middle of the cell, but not constant. The nucleus appears 

 to contain a distinct chromatic network in a definite membrane. 

 Besides, the epidermal cells are more frequently full of minute 

 rhabdites. 



The cilia covering all over the epidermis are much more 

 strongly developed ventrally than elsewhere. In some preserved 

 specimens the dorsal surface is often wholly destitute of them. In 

 fixation, they become matted together to form a tangled mass, in 

 wliich it is difficult to observe individual cilia. Where they are 

 inserted in the epidermis, tlie characteristic basal swellings give 

 the appearance of a very thin dense layer at the surface, which 

 has been interpreted by some investigators as a cuticula. 

 Although it is very difficult to determine the precise relation be- 

 tween the cilia and the protoplasmic striations of the epidermal 

 cells, the basal extensions of the former may probably be continu- 

 ous with the latter striations. 



Generally the epidermis comprises a number of interstitial 

 cells, usually known as Böhmig' s "Klebzellen," Avhich are charac- 

 terised by the perforation of the glandular ducts as well as by the 

 complete absence of cilia and rhabdites. The cells are more or 

 less higher than the general epidermal cells, and form a narrow 

 zone completely surrounding the body just within the lower 

 ventral margin. Tins submarginal zone is broad in the anterioi' 



