ii88 Puget Sound Marine Sta. Pub. Vol. 1, No. 26 



symmetrically arranged. Located within the abdomen of Petrolisthes eri- 

 omerus (Fig. 8), the male reproductive organs are found lying symmet- 

 rically on either side of the intestine (Fig. 8, int.). Each testis (^Fig. 8, 

 r. t. and I. t.) is a tubular mass from which is given off a long, thin, pro- 

 fusely coiling tube, the vas deferens (Fig. 8, r. v. d. and I. v. d.) which 

 runs to the base of the fifth thoracic leg (Fig. 8, /. I.) on the same side, 

 where it opens to the outside. 



4. HISTOLOGY OF THE VASA DEFERENTIA OF DECAPODA 



One who is familiar with the male reproductive elements of the De- 

 capoda knows that the mature spermatozoa as they are removed from the 

 vasa deferentia are usually found in pouches known as spermatophores, 

 and that these spermatophores are suspended in a thick whitish fluid which 

 is viscid in consistency. Now the question arises, how are these parts 

 produced? Dahlgren and Kepner (1908) in discussing the nidamental tis- 

 sues of crutacea have the following to say concerning these structures : 

 "Another form of male-carrying fluid is secreted by the spermatophoral 

 glands of certain crutaceans, as the lobster and the crayfish. This fluid 

 is secreted by the walls of the sperm ducts, and it not only serves as a 

 vehicle to carry the mass of sperm out of the male organs, but it also 

 forms a semifluid covering around them and attaches itself to a receiving 

 plate on the female body and hardens, preserving the life of the sperma- 

 tozoa for months or even years until they are needed to fertilize the eggs." 

 A histological study of the vas deferent ducts of the numerous Decapoda 

 already mentioned in the introductory remarks has revealed the fact that 

 in all these forms this sperm carrying fluid and the spermatophores are 

 elaborated by an internal layer of epithelium, which is more or less gland- 

 ular in nature. In some of these Decapoda this ejoithelial layer assumes 

 interesting modifications, and the cells may also bear cilia. 



A. The Vasa Deferentia of Anomura 



The Anomura studied were Lopholithodes mandtii and Pagurus seto- 

 sus. The vas deferens of Lopholithodes mandtii consists of five layers. (1) 

 a thin outer serosa of epithelium and (2) underneath this is a subserosa 

 of fibrous connective tissue. In most of the sections examined these first 

 two layers are sloughed off, due to the poor preservation of the material 

 from which the sections were made. Then follow two layers of smooth 

 muscle, one of which (3) is a circular layer (Fig. 11, c.) and the other 

 (4) a longitudinal one (Fig. 11, d.). Following these there is (5) a thin 

 inner layer of cuboidal epithelium (Fig. 11, e), which appears to be uni- 

 form throughout the tube. This inner epithelium secretes a thick fluid 

 which hardens into numerous wide, firm, convoluted membranes (Figs. 9-11, 



