THE SEMEN. 195 



matophori would be the homologues of the cells of other 

 glands, only in so far as they discharge an analogous func- 

 tion, and are secreting organs ; in the ulterior office allotted 

 to them, that of being receptacles in which the spermatozoa 

 are evolved, they stand alone in the animal economy, and are 

 certainly without analogues in any other gland of the body. 



It is most probable, however, that two kinds of cells 

 co-exist in the testes, the one secreting and corresponding 

 with the cells of other secerning organs ; the other kind, 

 of a peculiar nature, without parallel in the animal economy, 

 and devoted to the development of the spermatozoa. 



DEVELOPMENT OF THE SPEKMATOZOA. 



Not the least interesting part of the history of the sper- 

 matozoa is that having reference to their development. 



Wagner was the first to state that the spermatozoa are 

 developed within the spermatophori just described. 



This interesting discovery of Wagner has been amply 

 confirmed by the extended observations of Koelliker, Siebold, 

 Valentin, and Lallemand. 



Wagner thus describes the evolution of the spermatic ani- 

 malcules in the spermatophori of a bird. " In the course 

 of their development, a fine granular precipitate is ob- 

 served to form between the included nuclei, by which 

 these are first obscured and then made to disappear, and 

 linear groupings are produced, which anon proclaim them- 

 selves as bundles of spermatozoa, already recognizable by 

 slight traces of a spiral formation of one extremity. (See 

 Plate XVI. fig. 2. y.) It were hard to say whether the fine 

 granular precipitate is to be regarded as the product of a 

 process of resolution occurring to the nuclei, or a new form- 

 ation; as also, whether the spermatozoa spring out of or 

 only in and amidst the yolk-like matter, or matter that is 

 at all events comparable to the yolk of eggs in general. 

 The vesicles now assume an oval form" (see Plate XVI. 

 fig. 2. 7i), the globules disappear, the granular contents 



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