SEMEN. 



485 



Fig. 354,. Cephalopoda. In the Ce- 



phalopods we meet with the 

 former form of spermatozoa 

 with a distinct body and a thin 

 and long hair-like tail, as 

 among the scaly reptilia, &c. 

 The bod}' is cylindrical, or 

 staff-shaped, in the spermato- 

 zoa of Octopus vulgaris (Jig. 

 354.), which have a length 

 of i/", of which T A/ // belongs 

 to the anterior body. 



The spermatozoa in Sepiola 

 are shorter, and furnished 

 with a body which measures 

 i 'ff 



2"50 



The developement of these 

 spermatozoa occurs just as in 

 birds, according to Kolliker. 

 The separate spermatozoa 

 may be perceived very dis- 

 tinctly in the interior of their 

 cells of developement. The 

 fascicular grouping is want- 

 ing, although the spermatozoa 

 remain enclosed for some 

 time by the mother cells. 



These fibres in the Cepha- 

 lopods are, however, sur- 

 rounded in their passage 

 through the vas deferens 

 by peculiar sack-like enclosures or Sperma- 

 tophores, which are formed from the secre- 

 tions of the gland contained within the walls 

 of that channel. These enclosures gra- 

 dually assume a very strange complicated 

 structure, which we have only become ac- 

 quainted with, within a recent period, through 

 the excellent researches of Milne Edwards.* 

 They assume the shape of cylindrical bags of 

 a not inconsiderable size, so that they may 

 readily be perceived with the naked eye. They 

 contain at the posterior extremity a peculiar 

 apparatus (besides the Spermatozoa, which 

 are accumulated at the anterior thicker end), 

 which is distinguished by a particular me- 

 chanism adapted for the expulsion of the 

 seminal liquor. 



Gasteropoda. The spermatozoa of the Gas- 

 teropods exhibit, only in rare cases, as it seems, 



Spermatozoon of 

 Octopus vulgaris. 



Spermatozoa : A, of Patella ; B, of Chiton. 



a similar form to those of the Cephalopods. 

 This is the case, for instance, in Chiton and 



* Annales des Sciences Nat. 1842, tome xvii. 

 p. 335. 



Patella (fig. 355.). The spermatozoa of the 

 former consist of thin delicate fibres of -fa'", the 

 anterior body of which has an oblong shape, 

 measuring about -8<h/". The body in Chi- 

 ton is broader, almost pear-shaped, and of a 

 more considerable size Gtyo^O- Similar cer- 

 caria-like spermatozoa are possessed by Ha- 

 lyotis and Bermetus, as also by Trochus and 

 Paludina impura. The strict distinction be- 

 tween body and tail is, however, wanting in 

 most of the other Gasteropods. The sper- 

 matozoa then have a filiform shape, and in- 

 crease gradually in thickness from the pos- 

 terior, pointed, towards the anterior end. The 

 head or cephalic end is flattened. It is thus, 

 for instance, in Carinaria ; also among the 

 Nudibranchiata, Hypobranchiata, Pomato- 

 branchiata, and Pteropods. At the same time 

 the spermatozoon usually exhibits a num- 

 ber of light spiral windings, which diminish 

 uniformly from the anterior to the posterior end 

 (fig. 356. A). In Paludina vivipara (which, 



Fig. 356. 



1 * 



I 



Spermatozoa, A, of Doris B, of Paludina vivipara, 



from the form of the spermatozoa, likewise 

 belongs to this description, although the thin- 

 ner tail part is distinguished by a greater 

 length) the spiral windings are closer, as 

 among the singing birds, and confined to the 

 anterior body only (Jig. 356. B). The sperma- 

 tozoa of most of the other species of this genus 

 possess quite a different form. In Turbo, 

 Buccinum, Purpura, they are simply filiform, 

 and equally pointed towards both ends. In 

 Turbo they measure >"' ,V", in Thedys, 

 Aplysia T V /x/ > in Pleurobranchia Meckelii even 

 i /x/ , &c. 



The spermatozoa of pulmonary Gasteropods 

 are usually still larger, extending to 1'", 

 as in Helix. As in the Nudibranchiata, they 

 likewise become gradually enlarged toward's 

 the anterior part, but not flattened at the 

 cephalic end, being, on the contrary, fur- 

 nished with a short point (in Helix of T fo/"), 

 with an appendix, which must be viewed as 

 a peculiar form of body {fig. 357.). The same 

 is thickest at the posterior part, thicker than 

 the body, and gradually gets thinner to- 

 wards the end. In most cases (Helix, Arion, 



i i 3 



