SEMEN. 



487 



strongly, owing to its shape, of a group of cles are gradually produced, which continually 

 vorticellse (/%". 362.). increase in an endogenous manner, until the 



bursting of the mother cell, when the daughter 

 Fig. 361. Fig. 362. ce u s deposit themselves around the globular 



remainder of the cellular contents (Jig. 363.). 



Fig. 363. 



Spermatozoa of Helix po- A group of Spermatozoa 

 matia at their extrusion of Helix pomatia, 

 from the mother cell. partially protruded 



from the mother cell. 



As soon as the heads of the spermatozoa 

 have projected, the remainder of the mother 

 cell lengthens itself, and becomes a delicate 

 cylindrical envelope. These remains still ad- 

 here to the spermatozoa when completely ex- 

 tended, exhibiting the appearance of a couple 

 of larger or smaller knobs on the tail : the same 

 thing occurs in the spermatozoa of the frog. 



This mode of developement is not changed 

 by the presence of a greater number of sper- 

 matozoa in the interior of the mother cell. 

 All the difference that may be seen is, that 

 one spermatozoon comes forth rather earlier 

 than another. The free spermatozoa are, 

 however, by no means distributed without 

 order over the surface of the central globule 

 to which they still adhere. On the contrary, 

 they are grouped together into one com- 

 mon fasciculate mass, in the same manner as 

 we have already described in the singing 

 birds. This circumstance is remarkable, be- 

 cause it shows us that the formation of a 

 bundle of spermatozoa is not occasioned every- 

 where by the same means, and therefore 

 does not always justify the inference of the 

 persistence of an enclosing cell. 



A separation of the bundles of spermatozoa 

 happens in Helix : the central globule (which 

 forms the common cement that holds together 

 the individual spermatozoa, in the same way 

 as the tough albuminous mass in the cysts 

 of the singing birds) gradually passes away. 



The developement of the group of vesi- 

 cles in Helix is very interesting and im- 

 portant. It is at once apparent that the 

 same has originated from the brood of a 

 single, originally simple, cell, and that through 

 a continual endogenous increase. Our re- 

 searches have afforded us the immediate 

 proof of the truth of this, confirming, at the 

 same time, the conjecture of Kolliker ; 

 viz. that the primitive spermatic cells are the 

 same formations which have been described 

 as epithelial cells of the follicles of the testicle. 

 In the interior of these cells, the contents of 

 which consist of a brownish granular homo- 

 geneous substance, a certain number of vesi- 



Formation of groups of vesicles around the epithelial 

 cells of the testicle in Helix pomatia. 



The developement of the spermatozoa in the 

 other Gasteropods is similar to that describ- 

 ed, although not in all cases so distinct as 

 in Helix. The endogenous formation of the 

 spermatozoa can only with difficulty be per- 

 ceived in Lyma, Lymnaeus, &c. ; "it would 

 rather appear as if they were produced by 

 immediate growth from vesicular elements. 

 The general rule is, that they are united 

 with each other into groups, in which, how- 

 ever, the interior central globule is some- 

 times wanting (as in Cyclobranchiata, in 

 Turbo, Buccinum, &c.) ; but this does not 

 change in any way the developement and mode 

 of grouping together of the spermatozoa. 

 We have also, in this instance, in the united 

 vesicles of a group, unquestionably only the 

 brood of a common mother cell, which 

 group may have enlarged after the destruc- 

 tion of the external membrane that sur- 

 rounded it. The only difference would 

 consist, in the circumstance that the entire 

 contents of the mother cell are employed for 

 the structure of the daughter cells, leaving 

 no remainder, which perhaps might induce 

 a more firm connection of the separate vesi- 

 cles in the shape of a round mass. 



Acephala. In comparison with the variety 

 in the form of the spermatozoa among the 

 Gasteropods, we meet with but slight differ- 

 ences in the class of the Acephala, at least 

 among the Lamellibranchiates.* The sperma- 

 tozoa of these Mollusca consist of delicate 

 fibres of about 3^'" in length, the anterior end 

 of which supports a short and distinct body of 

 Fitr 364 variable size (from -oW 

 slo'") Ofr.364.)- This body 

 fj is usually (as in Unio, Cyclas, 



Clavagella) cylindrical ; in other 

 cases (for instance in Mytilus, 

 Pholas) pear-shaped. 



Respecting the formation of 

 these fibres we only know Kol- 

 liker's opinion of it, viz. that 

 they are produced in bundles 

 from round cellular masses, and 

 through an apparent prolonga- 

 tion of the vesicles ; as, for in- 

 stance, in Chiton, &c. : our ex- 

 amination of Unio was not 

 calculated to give us an insight into it. 



* VideV. Siebold in Mailer's Archiv. 1837, S. 381. 

 i i4 



