THE SEMEN. 197 



branes. When the spermatic animalcules have escaped 

 from the secondary cells, and these have disappeared, the 

 spermatozoa form a bundle which is still included within 

 the larger primary cell ; sometimes the seminal animacules 

 are irregularly disposed within its cavity, but more fre- 

 quently they are applied directly to each other, the heads 

 lying one way, and the tails in the opposite direction. 

 This disposition of them is often preserved even after their 

 escape from the spermatophori, during their stay in which 

 the spermatozoa usually remain quite motionless. 



The interesting and important fact of the development of 

 the spermatozoa in the secondary cells, or ova, as they should 

 now be called, Krclliker first ascertained by the study of 

 their evolution in the guinea-pig*; subsequently, he extended 

 his observations, and found that the spermatozoa in man were 

 evolved in a manner precisely similar. 



Valentin f during his inquiries observed masses of fila- 

 ments in the mother cells of the rabbit and bear, and Hall- 

 man | noticed the same thing in those of the rays ; he 

 does not however speak of the transformation of the included 

 nuclei or ova. 



In the class of invertebrate animals, it is most probable 

 that a similar method of development prevails. 



The spermatozoa are not encountered in equal numbers in 

 all parts of the testicle, the more remote convolutions of the 

 tubuli seminiferi containing chiefly the simple granular cells 

 and the spermatophori, while it is only in those which approach 

 near to the epididymis that they occur in any numbers ; in 

 this situation they usually lie immediately beneath the mem- 

 brane of the seminiferous tube, and external to the sperma- 

 tophori, their long axes being disposed in the direction of 

 that of the tube itself. In the vas deferens the spermatozoa 

 are present in vast numbers, and with scarcely any admix- 

 ture of /the other solid elements of the testes. 



It is in the epididymis that the different stages of de- 



* Beitrag. p. 56. tab. 11. fig. 20. f Report, p. 145. 1837. 



t Muller, Archiv. p. 471. 1840. 



R 4 



