498 



SEMEN. 



whilst the formation of the spermatozoa ' in 

 others (for instance, in Flustra, Erisia, 

 Bowerbankia) only commences when the 

 separate cells of clevelopement (B) have be- 

 come free through the destruction of the 

 large (-3-1^'" fa'") cyst-like mother cell (fig. 

 388. A.). The spermatozoa even here, how- 

 ever, are produced by the apparent growing 

 out of the small cells of developement (of 

 gi"'') containing nuclei (see ^g. 389.). When 

 developed they are linear and proportion- 

 ately thick and long (in Flustra about %'"'), 

 and frequently, it seems, furnished with a 

 roundish or oval corpuscle. 



Rotifcra The spermatozoa of the Rotifera, 

 at least of Megalotrocha, have a similar pin- 

 like form, if we may judge from the observa- 

 tion of KoUiker *, which is the only one before 

 us, and this does not seem to be quite decisive. 

 His statement, that these formations had par- 

 tially been fixed in the interior of the cavity 

 of the body, makes us at least look upon his 

 observations with mistrust, and leads us to 

 suppose that they have been confounded with 

 the remarkable vibratile organs, which are 

 certainly not spermatozoa. Kolliker' & observa- 

 tion, however, is interesting, inasmuch as he 

 also states that those fibres are apparently 

 produced through the growing out of small 

 solitary cells. 



Sperm atophora have not yet been met 

 with in the division of the Annelida. On the 

 other hand, however, we have observed that 

 the spermatozoa in some species of Saenuris 

 (Tubifex) unite into transparent homogeneous 

 strings (as in many insects) in their passage 

 through the vas deferens. These formations 

 have a cylindrical shape, almost vermicular, 

 getting thinner towards both ends. They are 

 also not unfrequently met with in the recepta- 

 culum seminis of the female apparatus. A simi- 

 lar mode of grouping seems to take place with 

 regard to the spermatozoa of the Hirudines, in 

 the so-called secondary testicles. The sper- 

 matozoa of the Nematoda (excepting the 

 paradoxical genus Pentastomum, in which we 

 find the ordinary linear spermatozoa) possess 

 very deviating shapes. They consist of a 

 roundish or oval corpuscle of about 3^'", 

 and a short rigid peduncle, which projects 

 more or less outwards, and has a varying 

 thickness (fig. 390.). The spermatozoa in 



Fig. 390. 



Spermatozoa of Strongylus auricularis. (After 

 Reichert in Miiller's Arcliiv. 1837. Tub. VI.) 



Gordius appear in the shape of short rods 

 without any corpuscles. 



We cannot doubt that these seminal ele- 

 ments are developed spermatozoa, having 

 sought in vain, and for a long time, for other 

 forms of developement, and having found 



* Froriep'a Neueu Notizen, S. 596. 



the very same formations again, in a perfectly 

 unchanged shape, in the female individuals. 

 We must therefore characterise Kiilliker's 

 supposition of these corpuscles being mere 

 stages of developement of seminal fibres, as 

 one that cannot be relied upon. 



The developement takes place in the same 

 way as in lulus. At first we find simple cells 

 containing nuclei, which, according to Rcichert's 

 researches, are produced in the interior of 

 large mother cells * (Jig. 391.). The nucleus 



Fig. 391. 



Spermatic cell of Ascaris acuminata, with four 

 vesicles of developement. (After Reichert.') 



has at first a roundish shape (fig. 392.), but 

 gradually stretches itself more and more, and 



t Fig. 392. 



Developement of the spermatozoa of Ascaris 

 acuminata. 



projects 'more or less outwards with its 

 point, thus metamorphosing itself into the 

 peduncle-like appendix of the spermatozoa, 

 the body of which is formed from the 

 persisting membrane of the seminal cell. This 

 last circumstance, but which does not in- 

 variably occur, is the only distinction that can 

 be found between the Nematoda and the 

 lulidae. 



RADIATA. Echinodermata. The sper- 

 matozoa, in the division of the Echi- 

 nodermata, possess, it seems throughout, a 

 pin-like form (Jig. 393.), with a small 



Fig. 393. 



Spermatozoon of Holothuria tubulosa. 



roundish body (of ^o'".)> anc ^ a ver J slender 

 tail appendix of about -fa'" -^'" . It is only 

 in rare cases (as Spatangus) that the body has 

 an oblong form, and is rather pointed at the 

 anterior end. 



The developing cells of these spermatozoa 

 are very small, and lie in groups, as in the 

 Bryozoa, inclosed in large cyst-like mother 

 cells. The developement of the spermatozoa 

 undoubtedly takes place according to the 

 usual mode, although it cannot be proved 

 with certainty, and although the appearance 



* Miiller's Arcliiv. 1847, S. 88. 



