292 LEUCKAET, ON MICROPYLE. 



4. Contact through premature dissolution of the vitel- 

 line membrane, as takes place, accoi'ding to Meissner, 

 for instance, in the Earthworm. The Gasteropoda, also, 

 in which a similar condition has been long known (vide 

 Lejdig. ' Zeitch. fiir wissenschaft. Zool. Bd.' ii. p. 127), 

 might probably be here included, as well, perhaps, as the 

 Hirudineae and others of the Invertebrata. 



What becomes of the spermatic filaments after they have 

 penetrated, and what particular part they may play in the 

 changes which we know immediately succeed the so-termed 

 impregnation, we are at present scarcely in a condition to 

 surmise. Tliis much only is known with certainty — that the 

 spermatic filaments, some of which enter the vitellus, whilst 

 some remain in immediate contiguity with it, between the 

 vitellus and its membrane, gradually dissolve (according to 

 Leuckart's observations in Melophagus and Epheviera^ far 

 more quickly than the filaments which remain external). 

 Whether this dissolution take place in consequence of a kind 

 of fatty metamorphosis, as Meissner states, or of a simple 

 disintegration and liquefaction, Leuckart is unwilling to de- 

 termine. It is sufficient to know that the filaments which 

 have entered are dissolved. But what farther becomes of 

 the remains of these fertilizing elements is at present wholly 

 unknown. It is highly probable that the substance of the 

 spermatic corpuscles, after their dissolution, becomes mixed 

 with the vitellus, but whether in a fluid or a molecular form 

 we know not — not knowing, even, whether this commixture be 

 deferred until impregnation is completed, and is conse- 

 quently, to a certain extent, only adventitious and incidental, 

 or whether it afford an impulse of some kind essential to the 

 process of impregnation and development. Still less, there- 

 fore, are we in a condition to determine whether, in the latter 

 case, the remains, whatever they may be, of the spermatic 

 filaments directly participate in any way in the formation of 

 the embryonic cells, or, indeed, in the construction of the 

 embryo. The demonstration of an immediate contact between 

 the spermatic filaments and the vitellus is undoubtedly an 

 important and interesting fact in the history of impregnation, 

 but one which, it is to be feared, will not soon be brought 

 within the compass of our sensual perceptions. 



