and Fertilization in the Nematoidea. 191 



duct itself. This mode of observation is certainly not to be ne- 

 gk^cted, in order to detect the nnitnal position of the different parts 

 of the contents; but it is not sufficient, as, on account of the 

 opacity [of the walls], it necessitates a tolerably strong pressure, 

 and consequently an injury to the object. AVhen the walls of the 

 oviduct are cut open under pure water, or slightly salt water, 

 which is better, so that the eggs tlow out without force, we do 

 not meet with the eggs with torn surfaces, which Nelson figures. 

 \Ve then see, also, that the adhesion of the seminal corpuscles 

 to the eggs is by no means so frequent as is asserted by the two 

 English observers. We may particularly convince ourselves 

 that this adhesion is effected solely by means of the flocculent 

 extremity. 



We therefore think that we must agree with Meissner, when 

 he disputes Nelson's description of the penetration of the semi- 

 nal corpuscle into the yelk. It still remains for us to examine 

 whether Meissner^s representation itself may have a greater 

 right to our supj)ort. 



It has already been shown that Meissner's micropyle does not 

 exist. This, however, by no means proves that the zoospermia 

 do not penetrate into the yelk exactly at the spot where Meissner 

 has supposed his so-called micropyle to be. Meissner asserts 

 that the seminal corpuscles adhere much more frequently on the 

 place of the pretended micropyle than on any other, and that 

 this adhesion is facilitated by the hood of the corpuscle. This 

 observer, as will be remembered, describes the formation of the 

 seminal corpuscles in a way very different from ours : he makes 

 the formation of the seminal corpuscle take place within the 

 development-cell. As it grows, it must acquire a crooked form, 

 until, suddenly extending itself, its anterior extremity passes 

 through the cell-membrane. In this way the latter is not lost, 

 but remains attached to the corpuscle as a hood. This hood we 

 have, however, been unable to see, and we must entirely dispute 

 its existence. Only once, amongst thousands of seminal cor- 

 puscles of Ascaris viystax, did one occur, which agreed pretty 

 well with .Meissner's figures, and was provided with a hood. 

 In this isolated case, however, we can only see an abnormal 

 formation. 



Meissner has figured several eggs upon the pretended micro- 

 pyle of which a seminal coi-puscle is seated. Without wishing 

 to doubt the correctness of the figures, we must still say, that 

 nothing of the kind has ever occurred to us. On the contrarv, 

 we repeatedly observed a phrenomenon in Ascaris suilla which 

 may perhaps throw a perfectly different light upon Meissner's 

 drawings. Thus, in unimpregnated females, ova are not unfrc- 

 quently met with, which, although their vitelline membrane id 



