Fecundation of the Ovum. 399 



at all eveuts in the animals observrd hy him, they dissolve and 

 unite to form a diop of oil, which must afterwards mingle with 

 the substance of the vitellus. Nelson had previously seen them 

 dissolve into a transparent fluid. But we may justly ask, 

 whether this be really their destiny, or whether it be not rather 

 the fate undergone by those which are not made use of, and which 

 would consequently be condemned to the fatty metamorphosis, 

 so common in animals, when Nature desires to facilitate the 

 absorption of useless materials. The spermatists may perhaps 

 some day raise their heads again, and again seek for their young 

 embryo in the spermatozoid ; the only object of which in seeking 

 to lodge itself in the ovum would then be, to tind a suitable 

 medium for its development. In the Earthworms, in which, as 

 we have seen, the eggs, on arriving in the couuuon recejjtacle, 

 float in a very considerable mass of semen, a large quantity of 

 the latter passes with the eggs into the capsule at the moment 

 of deposition. Those spermatozoids which have penetrated into 

 the vitellus become converted there into an oily fat, which 

 mingles with the elements of the vitellus ; the others, according 

 to Meissner, undergo the same metamorphosis, and remain in 

 the form of fat around the vitellus. Subsequently, by means of 

 their vibratile cilia, the embryos pass the whole of this fat into 

 their alimentary canal, in the same way that the embryos of the 

 Leeches consume their vitellus of nutrition. 



It remains now to be seen whether the new discoveries liave 

 caused the theory of fecundation to take a step forward. The 

 theory of the dynamists has not made any progress ; for to say 

 that the touching of an ovum by a spermatozoid awakens a 

 new life iu it, may be the expression of the fact, but is not an 

 explanation. Bischoff, who not long since supposed that the 

 essential part of the semen is the liquid itself, and that the 

 spermatozoa only prevented its decomposition by their move- 

 ments, has abandoned this opinion, and has the merit of having 

 introduced into science a new theory, which appears capable of 

 accounting for the facts, provisionally at any rate, in a more 

 satisfactory manner*. It is well known that Liebig admits the 

 existence in nature of a force analogous to the catalytic force of 

 Berzelius, his Jorcr of contact, by means of which he explains 

 various phsenomena which, without it, would be difficult to 

 understand. It consists in the fact that a body in a state of 

 chemical decomposition, or, to speak more correctly, a body the 

 molecules of which are in a state of chemical movement, is 

 capable of disturbing the chemical equilibrium of certain other 

 bodies, without adding anything to, or taking anything from 



* Ueber die Befruchtungstheorie. Miiller's Archiv, 184/. 



