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 body is cylindrical, or 

 staff-shaped, in the spermato- 

 zoa of Octopus vulgaris (fi<*. 

 354.), which have a length 

 of -J-'", of which liV" belongs 

 to the anterior body. 



The spermatozoa in Sepiola 

 are shorter, ami furnished 

 with a body which measures 



a-io'"- 



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- 



Spermatozoon of lo P odsare ' however, sur- 

 Octopus vulgaris. unded in their passage 

 through the vas deferena 

 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, 



1%. 355. 



J 



A 



El 



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



a similar form to those of the Cephalopoda. 

 This is the case, for instance, in Chiton and 



* Annales des Sciences Nat. 1842, tome xvii. 

 p. 335. 



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

 former consist of thin delicate fibres of -g^'", the 

 anterior body of which has an oblong shape, 

 measuring about ^fo/". The body in Chi- 

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

 more considerable size G^o // ")- Similar cer- 

 caria-like spermatozoa are possessed by Ha- 

 lyotis and Bermetus, as also by Troclms 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 Pterojtods. 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. 



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 '" fa'", in Thcdys, 

 Aplysia T L'", jn Pleurobranchia Meckelii even 

 A"' Sic 



6 > ***- 



The spermatozoa of pulmonary Gastcropods 

 are usually still larger, extending to \'" t 

 as in Helix. As in the Nudibranchiata, thev 

 likewise become gradually enlarged towards 

 the anterior part, but not flattened at the 

 cephalic end, being, on the contrary, fur- 

 nished with a short point (in Helix of ^.i-'"^ 

 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 



