132 THE PHYSIOLOGY OF THE COMMON CRAYFISH. 



nucleated cells, separated from the cavity of the organ by 

 a delicate structureless membrane. The growth of these 

 cells gives rise to papillary elevations which project into 

 the cavity of the ovary, and eventually become globular 



Fig. SH.—Astacus fliwiaUlis.—A, a lobule of the testis, showing; a, acini, 

 sprlng-ing from b, the ultimate termination of a duct ( x 50). B, 

 spermatic cells ; a, with an ordinary globular nucleus ra ; i, with a 

 spindle-shaped nucleus ; o, with two similar nuclei ; and d, with 

 a nucleus undergoing division ( x 600j. 



bodies attached by short stalks, and invested by the struc- 

 tureless membrane as a membrana propria (fig. 32, m). 

 These are the ovisacs. In the mass of cells which be- 

 comes the ovisac, one rapidly increases in size and 

 occupies the centre of the ovisac, while the others 



