TESTIS IN DECAPODOUS CRUSTACEA. 431- 



Iii the Macroura the testes commence on each side of the 

 stomach, and extend down to the middle parts of the abdomen. 

 In almost all the species of the section, these organs are 

 narrow ribbon-shaped organs, connected with one another 

 immediately behind the stomach by a narrow commissure ; 

 the vasa deferentia come off behind this commissure, and are 

 more distinct than in any other of the sections. In GalatJiea 

 these organs are more complicated, the tube being more 

 convoluted. 



The ultimate structure of the testis consists of a germinal 

 membrane, covered externally by the common tunic of the 

 organ, or by processes from it. The germinal membrane, in the 

 upper or first part of its course, developes from germinal spots 

 in its substance formative cells of a spherical shape and of 

 small size, which will be afterwards described. In the lower 

 part of the tube, the formative cells assume a peculiar linear 

 or spindle shape, attached by one of their extremities to the 

 germinal membrane, and projecting either into the cavity of 

 the gland-duct, as in Pagurus, or from its external surface as 

 in Crcdatlua, and therefore in this case covered by the common 

 enveloping tunic of the gland, or by processes of it which 

 correspond to the areolar vascular matrix of the glands in the 

 higher animals. 



When the animal is getting into season, numerous small 

 cells are found, as just described, on the internal surface of 

 the seminal tube, and more particularly from that portion of 

 the gland which lies on the surface of the liver. As the 

 animal becomes stronger, these cells increase in size from the 

 formation of young in their interior. That these young or 

 secondary cells are produced from the germinal spots on the 

 germinal membrane of the seminal tube, from which the 

 primary cell took its origin, appeared highly probable, among 

 other circumstances from this, that after the latter had burst, 

 its cell- wall was smooth and regular, not broken up or rough, 



