1917 Fasten: on Decapoda 291 



helliis (Fig. 18) it doesn't seem as if numerous spermatophores are devel- 

 oped. Here it appears that one large spermatophore is formed {Fig. 18, g) 

 in which the spermatozoa are tightly packed. 



The observations on the above Brachyura are in many ways similar 

 to those of Binford (1913). on the vas deferens and spermatophores of 

 the crab Menippe mercenaria. In discussing the vas deferent duct, on 

 page 149, Binford (1913) says: "The deferent duct is lined with a layer 

 of columnar epithelium which secretes the substance that forms the walls 

 of the spermatophores." In speaking of the spermatozoa in the vas defer- 

 ent duct this same author, on page 159 states, "The mature spermatozoa 

 pass from the tubules of the testis into the deferent duct. The latter is a 

 long, extensively folded tube lined with glandular epithelium. The sper- 

 matozoa form a common mass when they enter this tube, but the secretion 

 formed by its lining flows in among them and separates them into groups. 

 The secretion surrounding each group then hardens and so forms a mem- 

 brane, so that finally there are an immense number of capsules containing 

 the spermatozoa. These capsules are known as spermatophores. In this 

 condition the spermatozoa are transferred to the seminal receptacle of the 

 female crab." 



C. The Vasa Deferentia of Macrura 



The Macrura studied were Astacus leniiisculus, Homarus americanus 

 and Panulirus interruptiis. The vas deferent tubes of all these forms 

 agree in their general histological structure. There is (1) an outer fibrous 

 connective tissue coat (Figs. 21, 23-25, b), (2) a circular layer of smooth 

 muscle (Figs. 21, 23-25, c), and (3) an inner layer of columnar epithe- 

 lium (Figs. 21,^23-25, e) which contains cilia. 



In Astacus leniusculus the epithelial cells (Fig. 25, e) are more or 

 less uniform and some of them have been found to possess short cilia on 

 their free borders (See Figs. 26 and 27, h). The nuclei of the epithelial 

 cells are very prominent, as can be seen by studying Fig. 25. The large 

 imclei indicate that ths cells manufacture a great deal of secretion. These 

 secretions may be observed in various parts of the epithelial cells as vacuo- 

 . les or bubbles. They are especially evident on the surface of the cells 

 (See Fig. 25, e), and in the lumen of the vas deferens where they form 

 a dense viscid fluid (Fig. 25, /), that surrounds the spermatozoa (Fig. 25, 

 s). These heavy secretions in Astacus leniusculus appear to be of distinct 

 advantage to the species, for when the spermatozoa are passed to the out- 

 side, the surrounding secretions harden into firm, white, tube-like struc- 

 tures which adhere very tightly to the ventral surface of the female's 

 thorax, thereby preserving the life of the male germ cells until they are 

 needed for fertilization. 



