496 



SEMEN. 



other hand, are cell formations, which de- 

 velope a seminal fibre in the interior of the 

 enclosed nucleus. 



Of the same filiform shape, and probably 

 also of the same mode of developement, are the 

 seminal fibres of the Pychnogonides, which, 

 according to an observation of Kolliker, mea- 

 sure upon an average about -$'" in Pychno- 

 gonum Balsenarum. 



Equally filiform and also pointed at both 

 ends, are the developed spermatozoa of the 



Fig. 385. 



\ 



Developement of the Spermatozoa in Clitliamalus 

 PhUippii. (After Kolliker.} 



Cirripeds, the size of which, in Chthamalus 

 Philippii, amounts to about J^'" '. They are 

 produced from smaller nucleated cells (of 

 alo"' 3io"')> which would seem, from ex- 

 ternal appearances, simply to grow out into 

 seminal fibres (fig. 385.). An exact research 

 into the mode of their production is prevented 

 by the smallness of the cells ; but we need 

 the less hesitate in inferring the usual en- 

 dogenous mode of formation, since we know 

 how often spermatozoa, on liberating them- 

 selves from a mother cell, present, in a most 

 deceiving manner, the appearance of vesicles 

 that are growing out. 



Little is as yet known respecting the 

 spermatozoa of the Entomosiracct. Here also, 

 however, the usual filaments occur in the 

 seminal liquid, in some instances. This may 

 be proved in the genus Cypris, in which 

 such formations can readily be traced.* 

 They are of a considerable length (about 1"'), 

 and usually wrapped up in the shape of a reel. 

 Such a form of the spermatozoa does not, 

 however, seem to be the only one among the 

 Entomostraca. F. Siebold^, in Daphnia rec- 

 tirostris, describes oblong semilunar sper- 

 matozoa, whilst Cyclopsina, and probably 

 also Acanthocereus J, possess small finely 

 granular corpuscles of an oval shape, as the 

 elements of the semen. Similar corpus- 

 cles one of us (R. Leuckart with Dr. Frey ,) 



* We beg to direct attention to the simultaneous 

 appearance of eggs together with the spermatozoa 

 in the same individual ; and therefore to the her- 

 maphrodite condition of the genitals in Cypris. 



t Vergleich: Anat. S. 483. 



j According to Scholler, in Wiegman's Archiv., 

 1846, Th. i. S. 367. 



Ibid. p. 135. 



has discovered in Caligus. The production 

 of these elements, which could be observed in 

 the latter case, is the same as in lulus. They 

 at first appear as roundish nuclei in the in- 

 terior of the seminal cells, which have a size 

 of-rio'" SOT/"- At this period the nuclei 

 measure -$^5'" ; they subsequently grow, 

 change their shape to an oval, and in so doing 

 not unfrequently project outwards a little be- 

 yond the cell wall. 



Vesicular seminal elements are also pos- 

 sessed by Branchipus*, and oblong cylin- 

 drical corpuscles by Staurosoma.f 



In their passage through the vas deferens, 

 the spermatozoa in Cyclopsina, as well as in 

 the Cephalopoda, &c., are enclosed by one 

 common jelly-like spermatophore. In some 

 other cases, on the other hand (as in Onis- 

 cus), the spermatozoa unite into long flat rib- 

 bon-like strings (of I"'), which present quite 

 an uniform structure, betraying at the ends 

 only that they are composed of separate semi- 

 nal fibres.J 



_ Annelida. The spermatozoa, in the divi- 

 sion of the Annelida, also possess very gene- 

 rally a hair-like form, excepting among the 

 Nematoda. They are thin delicate fibres, ge- 

 nerally without any very considerable length 

 (in Hirudo J^"', Planaria varicosa ^'", in 

 Branchiobdella, on the contrary, quite '")> 

 which are either pointed towards the ends, 

 or every where equally thick (in the Tre- 

 matocla, Acanthocephala, and Cestoidea), or 

 enlarged at one end. 



In Lumbricus (fig. 386. A) the enlarged 

 part is of an oblong cylindrical form ; in the 

 Nemertinas (B) and the branchiated Annelida, 



Fig. 386. 



Spermatozoa of Lumbricus (A) ; ofNemertis Ehren- 

 bergii (B) ; and Planaria verrucata (c\ (After 



"""77"Z. \ *^ 



Aolli/ier.) 



on the other hand, they are round or pear- 

 shaped. In some few cases the spermatozoa 

 among the Annelida exhibit some spiral twin- 

 ings; as, for instance, in Planaria verru- 

 cata (c), Leptpplana atomata, and especially 



* Frey and Leuckart in Wagner's Zootomie, 2d 

 edit. Part II. p. 259. 



f Will in Wiegman's Archiv., 1844, Th. I. 

 S. 340. 



J Vide Siebold in Mailer's Archiv. 1836. 



