XXXV] TISSUES OF REPRODUCTION 283 



remaining cells into columns. The spermatogenic cells 

 are smaller and form an irregular double row. 



c. Tubes with the heads of the spermatozoa in 

 groups at various levels from that of the spermatogenic 

 cells outwards. 



10. Transverse section of the vas deferens. Note 

 The thick outer longitudinal and inner circular 



muscular coat. 



The mucous coat, slightly folded, without glands ; 

 the epithelium cells are columnar and have no cilia. 



11. Spermatozoa. Cut in half the fresh testis of 

 a rat or mouse, and gently press the cut surface on a 

 glass slide. Observe the spermatozoa, each consisting of 



A head or body. 

 A long tapering tail or process. 

 A short intermediate part. 



Note that the spermatozoa move by a whip-like 

 movement of their tails. 



12. Observe in like manner the spermatozoa of a frog or newt 

 in the spring. The head is long and pointed, the intermediate 

 part small and not very distinct; from the intermediate part 

 starts a filament which runs in a spiral around the long tail; 

 the filament is at the edge of a thin spiral membrane, but this is 

 difficult to make out. 



DEMONSTRATIONS. 



1. Section of young ovary. Note the germinal 

 epithelium dipping down from the surface to form the 

 ovarial tubes. 



2. Section of vagina (dog or cat; potassium bi- 

 chromate). Note the epithelium consisting of several 



