2l6 



THE BIOLOGY OF THE FROG 



CHAP. 



lining of cells, some of which (spermatogonia^ spermatocytes, 

 and spermatids) represent stages in the formation of sperma- 

 tozoa ; others form the so-called " follicle-cells," and the 

 flattened cells described by Bertacchini, which lie next to 



FlG. 59. A, cross section of one of the tubules of the testis ; sp, bundles of 

 spermatozoa; t.e, epithelial lining of the tubule. B, stages in the de- 

 velopment of spermatozoa. (After Parker and Parker.) 



the outer membrane. The follicle cells form a sort of wall 

 around groups of cells from which the spermatozoa take 

 their origin. 



The spermatozoa of the frog pass through the substance 

 of the kidney into the ureter. In many species of frogs the 

 free portion of the ureter is dilated to form a seminal recep- 

 tacle in which the spermatozoa are stored against the time 

 of their discharge from the body. The seminal receptacle 

 is poorly developed in Rana pipiens and R. Catesbiana. In 

 the European species R. fusca it becomes very large and 

 divided into a number of compartments. 



Corresponding to the various stages in the development 



