1917 Fasten: on Decapoda 289 



/) from which are suspended the spermatophores (Figs. 9-11, g) filled with 

 the mature spermatozoa. These spermatophores are formed from the same 

 secretion as the membranes, and many of them are usually found in a row 

 attached to the membrane wall (See Figs. 9 and 10, g). 



When a portion of the vas deferens of LopholitJiodes mandtii is cleared 

 and examined in its entirety (Fig. 6), it appears as if the interior con- 

 sists of numerous tubes (Fig. 6, f) which are enclosed in a large outer 

 investing tube (Fig. 6, g). A study of longitudinal (Fig. 10) and cross- 

 sections (Fig. 9), however, reveals the true nature of these structures. 

 The investing tube (Figs. 6, 9 and 10, j) is then recognized as the vas 

 deferent tube proper, while what appears to be the numerous internal 

 tubes (Figs. 6, 9, 10 and 11, /) are not tubes at all, but are convoluted 

 membranes with suspended spermatophores, the structures formed from 

 the secretions of the lining epithelium. 



In Pagurus setosus (Figs. 12-16), one of the true hermit crabs, the 

 vas deferens is made up of the same structures as the vas deferens of 

 Lopholithodes mandtii. Owing to the better preservation of the material 

 from Pagurus setosus, the five layers (Figs. 14-16, a, h, c, d, e) are seen 

 more distinctly, especially the first two layers, namely, the serosa (Figs. 

 14-16, a) and the suberosa (Figs. 14-16, b). In Pagurus setosus the in- 

 terior epithelium becomes somewhat modified. Here, throughout most of 

 the vas deferent tube the epithelium is thin and uniform, and consists 

 of a single layer of ciliated cuboidal cells (See Fig. 16, e). However, 

 at one point of the tube the epithelial cells become concentrated into a 

 mass of elongated columnar cells bearing prominent nuclei and also pos- 

 sessing very fine examples of cilia from their free borders (See Figs. 14, 

 15, 28, 29, e and h). In Figs. 28 and 29, which are microphotographs 

 of cross sections of some of the epithelial cells in this region taken under 

 a high magnification, the cilia are seen very prominently. In Fig. 28 

 many of these cilia are found clinging together into "brushes." In Fig. 29 

 the individual cilia are especially well seen. These cilia arise from a dis- 

 tinct border; they possess basal granules, and in many instances they 

 may be followed down into the cytoplasm of the cells. 



This concentrated region of epithelium appears to be the place where 

 roost of the internal secretion is elaborated. This secretion is also laid 

 down somewhat differently than in Lopholithodes mandtii. In Pagurus 

 setosus the elaborated membranes are not nearly as convoluted, being de- 

 posited in layers which harden into more or less straight sheaths (Figs. 

 12-14, f). The spermatophores (Figs. 12-14, g) may be observed tightly 

 wedged into the spaces between these sheath-like membranes. 



