ANATOMY AND DEVELOPMENT OP PERIPATUS OAPENSIS. 2-37 



division elsewhere though it is not so easy to see. It is to be 

 presumed that the cuticle is regularly shed. 



The epidermis, placed immediately within the cuticle, is 

 composed of a single row of cells, which vary, however, a good 

 deal in size in different regions of the body. The cells excrete 

 the cuticle, and, as shown in fig. 32, they stand in a very 

 remarkable relation to the secondary papillae of the cuticle just 

 described. Each epidermis cell is in fact placed within one of 

 these secondary papillae, so that the cuticle of each secondary 

 papilla is the product of a single epidermis cell. This relation 

 is easily seen in section, Avhile it may also be beautifully shown 

 by taking a part of the skin which is not too much pigmented, 

 and, after staining it, examining from the surface. 



In fig. 32 a region of the epidermis is figured, in which the 

 cells are exceptionally columnar. The cuticle has, moreover, 

 in the process of cutting the section, been somewhat raised 

 and carried away from the subjacent cells. The cells of the 

 epidermis are provided with large oval nuclei, which contain a 

 well developed reticulum, giving with low powers a very gra- 

 nular appearance to the nuclei. The protoplasm of the cells 

 is also somewhat granular, and the granules are frequently so 

 disposed as to produce a very well-marked appearance of stria- 

 tion on the inner end of the cells. The pigment which gives 

 the characteristic colour to the skin is deposited in the proto- 

 plasm of the outer ends of the cells in the form of small 

 granules. An attempt is made to show this in fig. 32. 



At the apex of most, if not all, the primary wart-like papillae 

 there are present oval aggregations, or masses of epidermis 

 cells, each such mass being enclosed in a thickish capsule (fig. 

 31). The cells of these masses appear to form the wall of a 

 cavity which leads into the hollow interior of a long spine. 

 These spines when carefully examined with high objectives 

 present a rather peculiar structure. The base of the spine is 

 enveloped by the normal cuticle, but the spine itself, which 

 terminates in a very fine point, appears, as shown in fig. 31, to 

 be continuous with the inner layer of the cuticle. In the 

 perioral region the outer layer of the cuticle, as well as the 



