SEMEN. 



501 



This connexion is, however, least distinct 

 among the higher Vertebrata ; in which, inde- 

 pendently of the spermatic cells which exist 

 free in the semen of the seminal canals, there 

 likewise occurs a special and generally 

 well developed stratum of epithelial cells, 

 which are distinguished from the former by 

 size and appearance. But this arrangement 

 is only to be met with during the period of 

 generative maturity. Previous to it, free 

 spermatic cells do not exist, and the canals of 

 the testicle have then uniform contents, con- 

 sisting of small cells of ^ of a line in dia- 

 meter, in which one or two small granules 

 are contained. We have not been able to 

 trace the history of the real seminal cells, but 

 we do not consider it as altogether impro- 

 bable that they are produced from the former 

 epithelial cells, and most likely are developed 

 in an endogenous manner. The possibility 

 can certainly not be denied, that they may 

 have been produced independently and free 

 in the interior of the seminal canals. But 

 even in this latter case it is unquestionable 

 that the vesicle in which they develope 

 themselves is furnished by the epithelial cells 

 and has formerly been contained in their in- 

 terior. The difference even in this instance, 

 therefore, would not be so very material, and 

 might be reduced to a mere difference in the 

 periods of formation. In both cases the 

 seminal cells might be assumed to be produced 

 from the contents of the epithelial vesicles, 

 either at a period when such contents are still 

 contained in the interior of them, or after 

 they have become free. 



Our preceding remarks respecting the his- 

 tological relations of the seminal cells apply 

 in an equal measure to all animals, and not 

 merely to those the spermatozoa of which 

 possess a linear form and are produced in 

 the interior of the vesicles of developement. 

 The Chilopoda, Acarina, Entomostraca, and 

 Nematoda furnish us with sufficient proofs 

 of this, proofs which contradict the as- 

 sumption of JTo/fifcr#,that a linear form of 

 spermatozoa is common to all animals. Al- 

 though many of the differently-shaped seminal 

 elements may, after a more accurate research, 

 be proved to be mere forms of developement 

 of the real spermatozoa, even this cannot be 

 asserted with regard to all of them. These 

 differently- shaped seminal elements are the 

 very ones that here more particularly concern 

 us ; we know that they differ in their develope- 

 ment from the ordinary seminal fibres. They 

 are solid massive corpuscles, which, as we 

 have already shown, have been produced 

 simply and immediately from a metamorphosis 

 of nuclei. 



But even here it is the nuclei of the seminal 

 cells, which serve for the developement of the 

 spermatozoa. The whole difference consists 

 in this, that the nuclei are metamorphosed 

 altogether into the fructifying elements of the 

 semen, whilst otherwise they produce the 

 spermatozoa in the interior, they themselves 



* Page 63. 



getting dissolved when the latter are about 

 to be liberated. The external cellular mem- 

 brane which encloses these nuclei remains, 

 however, without any immediate participation 

 in the formation of the spermatozoa. It gets 

 destroyed in the course of the developement, 

 in order to enable the nuclei, which in the 

 mean time have been converted into sperma- 

 tozoa, to make their exit. This at least holds 

 good in most of these cases, the Nematoda 

 only being an exception. The membrane of 

 the cells belonging to the metamorphosed 

 nuclei, persists in the latter-named animals. 



According to this we have a threefold mode 

 of developement of the spermatozoa, viz.: 

 1st. The cell membrane and nucleus of the 

 formative vesicles convert themselves imme- 

 diately into the spermatozoon. 



2d. The nucleus of the formative vesicles 

 alone metamorphoses itself into the sperma- 

 tozoon. 



3d. A new formation, which takes place in 

 the interior of the nucleus (or immediately in 

 the cell cavity), performs the functions of 

 a spermatozoon. 



On comparing the spermatozoa developed 

 in these different ways, we cannot deny that 

 they have a different stage of developement 

 in a morphological point of view. The sper- 

 matozoa resulting from endogenous forma- 

 tion are most highly developed ; they are the 

 produce of a perfectly new generative process, 

 whilst the other forms of spermatozoa owe 

 their origin to a persistency and further 

 developement of structures, which, first of all, 

 were mere transitory elements, and were only 

 of importance as the seat of that neoplastic 

 process. Under such circumstances we may 

 assume, then, that all these forms of sperma- 

 tozoa, according to the morphological rela- 

 tion in which they stand, are mere different 

 stages of developement in one common coi> 

 tinued series, mere variations of one thema, 

 in which the differences seen are not essen- 

 tial, but only of a relative import. Taking 

 into consideration this unity, we cannot 

 agree to the objection that may possibly 

 be made to us, as if we had described the 

 spermatozoa (which, essentially and in fact, 

 are identical formations) to have been pro- 

 duced in different ways. The mutual rela- 

 tion of these differences is in- perfect unison 

 with the laws of organic architecture, which 

 every where (when a common plan is made 

 the basis of a series of formations} exhibits 

 the variety of the concrete form principally 

 through a variable developement and perfec- 

 tion of the ideal type. 



It might not be without interest to re- 

 flect upon the important part which the 

 nucleus plays in the formation of the sperma- 

 tozoa, since it is an element which is usually 

 only important for the formation of cells, and 

 does not participate in their subsequent me- 

 tamorphoses. This at least is the rule ; 

 a rule, however, by no means without excep- 

 tion. We already know that in many cases 

 the nucleus is important for the developement 

 of certain parts ; we know that the nucleus 



K K 3 



