and its relation to that in the Animal Kingdom. 441 



It is extremely probable that the mass of the corpuscles becomes, 

 after solution, mixed with the vitellus, but whether as fluid, 

 or in the form of molecules, we know not ; we do not even know 

 whether this mixture takes place only after the completion of 

 the fecundation, or whether it constitutes some essential element 

 of the processes of fecundation and development. Still less, of 

 course, can we judge whether, in the last case, any remnants of 

 the spermatozoids take a direct part in any way in the formation 

 of the embryonal cells, or in the evolution of the embryo/^ 



The former of the two cases here referred to is in favour of the 

 hitherto current theory as to the essential nature of the fecundating 

 process, in accordance with which the spermatozoids perform 

 merely the part of a ferment. Meissner* declares decidedly for 

 the latter. He thinks we may imagine that the changing sper- 

 matic elements, like fermenting bodies, may excite in the vitellus, 

 with which, as we now know, they come into direct contact, move- 

 ments — the immediately commencing phsenomena of develop- 

 ment — and that at the same time their component parts, which 

 remain in the ovum, do not undergo changes independently of 

 the vitellus, but become at last blended with the parts of this 

 (into an embryonal yelk, as Nelson called it), and constitute a 

 material portion of that which becomes developed into the em- 

 bryo ; he regards the process of fecundation neither as a simple 

 chemical process, nor as a simple contact-action, but as a pro- 

 cess sui genei'isj which exhibits traces of the presence of both, 

 but yet is itself neither one nor the other. 



Obscure as are at present our conceptions therefore as to the 

 essential nature of the process of fecundation, yet the existing 

 observations appear to me to give satisfactory evidence of two 

 things: first, of the error of Burmeistert, when he regarded 

 " the male molecular element (spermatozoid) no longer as merely 

 constitutmg the vivifying agent in fecundation, but even as the 

 ^ci\xdi\ primitive germ, the primary rudiment of the new organism,^' 

 and considered '^ the female individual really as the alma mater, 

 which rears, nourishes, and developes the germ delivered to her 

 as a formally and materially determinate rudiment,^^ — an error 

 which SchachtJ has also adopted, on which account alone I of 

 course come to speak of it here. From other quarters, besides 

 those above cited, facts come to oppose this hypothesis : the 

 independent, if not ordinarily very far-extended expression of 

 the developmental force which has its seat in the ovum, the 

 segmentation and formal development of embryos in unfecun- 



* Siebold u. KoUiker's Zeitschr. f. wiss. Zoologie, Bd. vi. Heft ii. p. 259 

 et seq., 1854. 

 t Abhandl. Nat. Ges. zii Halle. 2 Bd. 3 Quartal. pp. 18.9, 190. 

 X Ueb. Befrucht. der Pedicularis sylvat. Flora, 1855, p. 471. 



