SEMEN. 



477 



either singly (Jig. 326. D) or in numbers of three 

 four, six, or seven (fig. 326. E). A more con- 



Fig. 326. 



Developing Vesicles of the Spermatozoa from the 

 Testicles of the Dog. 



siderable number of them in one common cyst 

 is unusual ; but they may, according to Kol- 

 liker's statement, amount to twenty. The size 

 of the cyst naturally depends on the number 

 and state of developement of the vesicles it 



encloses. Ordinarily it amounts to about 

 i /// i /// 



ToW so . 



On pursuing the genesis of the vesicles of 

 developement, it will be found that they are 

 produced in the interior of cells, according to 

 the law of endogenous formation. The various 

 circumstances which present themselves during 

 the microscopical analysis support the proba- 

 bility of this opinion. It is certainly often 

 difficult to determine whether an individual 

 vesicle is destined for the production of other 

 cells (tochter-Zellen), or immediately for the 

 formation of a spermatozoon. But we shall 

 see presently that the daughter cells are fur- 

 nished with the same capacities as the free 

 vesicles of developement ; they are like them 

 in every respect, and justify the inference of a 

 perfect identity with them. Wherever, there- 

 fore , we find these free vesicles of developement, 

 they have, in our opinion, likewise been pro- 

 duced in the interior of other cellular forma- 

 tions, and have only become free by the dis- 

 solution of the former. The real process of 

 formation of the spermatozoa in the interior of 

 the vesicles of developement cannot be reached 

 by our observation. The spermatozoon does 

 not possess at its commencement those sharp, 

 distinct contours that great refracting power, 

 which afterwards so much distinguish it. Like 

 a slight linear shadow it is seen lying in the in- 

 terior (fig. 327. A, B) ; in addition to which it 



Fig. 327. 



Spermatozoa of the Dog in the interior of the 

 developing Cell. 



is covered by the granules, which are so readily 

 deposited from the liquid part of the con- 



tents. It is only gradually that it assumes a 

 distinct appearance. At first the body only 

 is seen, being recognisable by its specific 

 form. The tail becomes visible subsequently. 

 The entire spermatozoon lies in a curved 

 shape close to the wall of the vesicle, until it 

 has reached its full developement, when it be- 

 comes free by the bursting of the vesicle of 

 developement. Sometimes (fig. 327. C,D) indi- 

 vidual vesicles may be seen, from which the 

 tail of a spermatozoon is projecting, whilst the 

 body is still situated in the interior. The vesicle 

 of developement generally retains, however, 

 its original round shape, even when the sper- 

 matozoon has reached its perfect developement, 

 and begins to stretch itself. Angular vesicles 

 of developement, which occur so frequently 

 in other animals, probably never occur here. 

 It is only in rare cases (fig. 327. D) that the 

 vesicle extends itself into a thin tail-like 

 appendix, which then encloses the posterior 

 part of a spermatozoon, and which is 

 evidently only produced by the stretching 

 of the latter. A law, which Kolliker first 

 pronounced as correct, may here be enume- 

 rated, viz. that only one single spermatozoon, 

 and never a greater number, is developed in 

 each vesicle of developement. 



The formation of the spermatozoa takes 

 place in exactly the same way in the vesicles 

 of developement, even in those cases where the 

 latter have not become free, but remained 

 enveloped by their mother cells. The sper- 

 matozoa, in this case, are not, however, im- 

 mediately set free by the dissolution of 

 the vesicles of developement ; but they ar- 

 rive, first of all, in the cavity of the ex- 

 ternal cyst. The number of the enclosed 

 spermatozoa therefore depends on the num- 

 ber of the enclosed vesicles of develope- 

 ment, a single fibre only being formed in 

 each vesicle. The presence of several sper- 

 matozoa in the interior of a vesicle, therefore, 

 affords us an immediate proof, that the latter 

 histologically possesses the function of a 

 mother cell, and is not itself the vesicle of 

 developement. 



But likewise in this case the process ter- 

 minates with the dissolution of the cyst that 

 surrounds the spermatozoa, and which pre- 

 vented their becoming free immediately after 

 the dissolution of the vesicle of developement. 



According to analogy with other animals, 

 it is very probable that the above men- 

 tioned association of groups of the sperma- 

 tozoa into fascicles is caused by the longer per- 

 sistency of the vesicles of developement in the 

 interior of a common mother cell. At all 

 events, such an occurrence is traceable in 

 almost all other cases in which a similar asso- 

 ciation in groups takes place; and it also 

 happens among the mammalia, to judge from 

 the fact, that a delicate cyst-like enclosure is 

 often perceived at the circumference of the 

 bundles. 



AVES. The spermatozoa of birds possess 

 uniformly, instead of the short oval and flat- 

 tened body which distinguishes them in 

 mammalia, a body of a long and slender 



