10 Journal of Comparative Neurology. 



reaches a nerve are so few that I would not, perhaps, be justi- 

 fied in deciding that such a process never branches. Each cen- 

 tral process is slightly sinuous in its course ; it takes such stains 

 as Kleinenberg's haematoxylin but lightly, appears finely gran- 

 ular, and is of uniform diameter. With the methylene blue 

 method it becomes delicately beaded or coarsely varicose. In 

 fact, it presents all the characteristic appearances of a nerve- 

 fiber. All the central processes, or axis cylinders, which come 

 from the same group of nerve-cells — i. e. , from a single sense- 

 organ — pass together in a slender bundle between the central 

 ends of the epidermal cells to the base of the epidermis. 



In the base of the epidermis, as is easily seen in sections, 

 are many nerve bundles which can be traced directly into the 

 central nervous system. Even when a cell in one of the diffuse 

 sense-organs is stained intensely blue, it usually happens, in my 

 preparations, that the central process itself is stained for only a 

 short distance centrally from its cell. Moreover, the entire 

 bundle of nerve-fibers from one sense-organ is not only very 

 slender, but always passes to the base of the epidermis in a 

 more or less undulating course so that it is often cut obHquely. 

 These facts render it usually impossible to trace either a single 

 peripheral process or the entire bundle itself into one of the 

 epidermal nerves. In two cases, however, the bundle of cen- 

 tral nerve-fibers from an organ turned obliquely in the plane of 

 the section and entered a cross section of an epidermal nerve 

 (Plate II, Fig. 30). Moreover a central process itself in each 

 of these bundles was stained blue for a longer distance than 

 usual and could, therefore, be traced continuously. These two 

 cases may be taken as evidence, it seems to me, that the central 

 processes from all the diffuse sense-organs enter the nerves lying 

 in the base of the epidermis. As v/ill be seen later, this con- 

 clusion is abundantly supported by a study of the diffuse sense- 

 organs of the various tactile appendages. In these it is clearly 

 seen that all the central processes pass directly into nerves 

 which in turn pass directly into the central nervous system. 



The peripheral end of each cell gives rise also to but a 

 single process. The latter passes, in company with the other 



