SIXTEN BOCK, TWO NEW COTYL. GEN. OF POLYCLADS. 23 



Anatomical description. 



Body-wall. The external epithelium is rather low for a 

 polyclad, 10 »j- or less, and consists of very broad cells which 

 gives it an unusual appearance for a polyclad. The nuclei 

 are, in accordance with the shape of the cells, spherical and 

 comparatively large (4 {j.). Epithelial gland cells are extreme- 

 ly few. The epithelium is thus more like that of the 

 alloeocoelean turbellarians than that of any polyclad. To 

 this similarity is to be attributed the exceptional fact, 

 for a polyclad, that the rhabdite-cells are removed to the 

 subdermal layers. 



The same kind of sensorial cells as I have described for 

 Cryptocelides Loveni Brgdl (Bock, 1913, Taf. VI, Fig. 17) 

 occur in the dorsa) epithelium of Amyella, i. e. shorter cells 

 with long tufts of cilia. Through these cells small depres- 

 sions in the outline of the epithelium are formed. I have 

 further observed on the ventral epithelium a wavy contour 

 produced by a shorter length of a part of the ordinary 

 epithelial cells. 



The basement membrane is thin and the muscular wall 

 of the body is, like that of Cliromoplana, inconsiderable. This 

 feeble development of the muscularis differs remarkably from 

 the typical conditions of the polyclads, in which group the 

 different layers are very distinct, thick and compact. The 

 muscularis of Amyella as well as that of CÄromop/a7ia resem- 

 bles that of the alloeocoelean turbellarians. 



Nearly all the pigment of Amyella is subdermal and in 

 this respect it differs from the conditions in Chromoplana. 



The rhabdites seem exclusively to be formed in sub- 

 dermal gland -cells. These subepithelial cells are scarce on 

 the ventral side, but rather numerous on the dorsal side. In 

 the anterior part of the body they occur in more consider- 

 able numbers. 



This is the first known example of subdermal rhabdite 

 cells occurring in the polyclads. Lang points out that the 

 exclusive occurrence of the rhabdites in the epithelium is 

 just one of the facts which indicate the primitiveness of the 

 polyclads in comparison with the other turbellarians. It is 

 therefore rather interesting to find that a polyclad genus, 

 and a considerably specialized one, possesses true subdermal 



