IN THE DECAP0DOUS CRUSTACEA. 37 



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 Galcitliea 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 Galathea, and therefore 

 in this case covered by the common enveloping tunic of the 

 gland, or by processes of it which correspond to the areolar vas- 

 cular 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 cells 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, as might have been expected, had the secondary 

 cells been formed from it. After these primary cells have burst, 

 the secondary cells contained in them pass down the seminal tube, 

 to undergo the changes to be afterwards described. 



The spindle-shaped cells in the lower part of the seminal tube 

 are large primary cells, two or three generally arising from a 

 disk or spot in the germinal membrane. They correspond in 

 every respect, except in shape and size, to the spherical primary 

 cells further up the tube, and like them form in their interior 

 young or secondary cells. These secondary cells originate in a 



