Contributions to the Anatomy and Histology of Thalassema neptuni Gaertner. 539 



or clear cells , so that in this point one may be led into 

 error. 



1) The typical epidermal cells (Fig. 1, 2, 5, 6 ep. c), cylindrical 

 cells, or "Fadenzellen". At their insertion on the cuticle these cells 

 form a very typical mosaic-like structure (Fig. 4), being irregularly 

 polygonal in surface section, with margins which are apposed except 

 where the glands open out between them. But immediately we 

 examine horizontal sections a short distance below the cuticle they 

 lose their simple relations. In such sections we find that they form 

 a reticulum, in the meshes of which lie the gland cells, clear cells, 

 and a number of intercellular spaces (Fig. 5). The deeper we follow 

 the "Fadenzellen" the smaller they become in relation to the other 

 elements so that on longitudinal or transverse sections of the papillae 

 they appear almost thread-like in their basal parts. 



Below the level of their nuclei they end in root-like processes 

 which are connected with one another, or bury themselves in the sub- 

 jacent cutis. This is a very typical form of epidermal cell among the 

 Annelids in general. I have in no case been able to determine the 

 presence of a direct connexion between these cells and fibres of 

 connective tissue or nervous origin such as Greeff (6), and Rietsch 

 (12) describe. 



Greeff's description refers to Echiurus pallasii. He speaks of 

 these cells as "Cylinderzellen , die mit äussern , abgestumpften End- 

 flächen mosaikartig an einander grenzen und , nach innen sich zu- 

 spitzend, in ein fadenförmiges Ende auslaufen, das an einigen Stellen 

 der Haut, namentlich an den später zu beschreibenden Hautpapillen, 

 direct in das Bindegewebs- und Nervenfadennetz der folgenden Schicht 

 überzugehen scheint" (p. 43). Rietsch's account is very much more full. 

 He describes what he believes to be a "réseau gaughonnaire" which is 

 composed of "cellules ganglionnaires anastomosées entre elles"; this 

 "rosea u", sends distal processes, which connect with the epidermal cells, 

 and proximal processes, which in Bonellia minor he has not been able 

 to trace to nerves, although he says it is easy in Thalassema neptuni 

 to see this connexion. I believe, as I have stated above, that this 

 appearance is due to the distortion and compression of the tissues 

 owing to the immense development of the gland cells. I have myself 

 very often seen a structure that one could interpret as a "réseau 

 ganglionnaire" comparable to Rietscii's figure (12, tab. 17, fig. 2), but 

 in all cases it was due to the root -like processes of the epidermal 

 cells themselves being somewhat tangentially cut. The object of such 



