and Fertilization in the Nematoidea. 193 



set up by Meissner stands upon a very weak footing, as will be 

 shown immediately. 



Both Nelson and Meissner saw the seminal corpuscles undergo 

 very important alterations after their penetration into the yelk. 

 According to Nelson^s statement, they lose their characteristic 

 form, and become converted at last into irregular, transparent, 

 but strongly refractive masses. Meissner groups these changes 

 together as a gradual fatty metamorphosis. According to him, 

 the seminal corpuscle gradually undergoes a conversion into a 

 drop of fat. 



At the first glance we cannot avoid seeing a great concordance 

 in the representations of the two writers, — a concordance which 

 must apparently be indicated as in favour of the observation, all 

 the more because in other respects the two observers above men- 

 tioned do not usually take the same path. This agreement is, 

 however, only apparent. It will be remembered that Nelson 

 supposed that in every female a certain number of ova escape 

 fecundation. These are his "false eggs." According to Nel- 

 son's statement, symptoms of retrogression soon appear in them. 

 The germinal vesicle disappears, and in its place a certain num- 

 ber of transparent globules, which look like oil- drops, make their 

 appearance. The author thinks that these globules are a pro- 

 duct, on the one hand, of the germinal vesicle that has dis- 

 appeared, and, on the other, of an incipient separation between 

 the vitelline oil and granules. He adds, that these drops cannot 

 be confounded with the small masses produced by the conversion 

 of the seminal corpuscles, because the latter are of an irregular 

 form, and never exhibit the uniform outline of an oil-drop. 



We now see that the oil-drops in Nelson's "false eggs'' have 

 a much greater resemblance to Meissner's zoospermia converted 

 into fat, than the masses which are produced, according to 

 Nelson, by the metamorphosis of the zoospermia. Meissner 

 has also acknowledged this, and for this reason he denies that 

 Nelson's " false eggs" were unfecundated. The oil-drops con- 

 tained therein are, with him, metamorphosed seminal corpuscles. 



Amongst all these mutually contradictory statements we are 

 in a position to confirm only those of Nelson with regard to his 

 " false eggs" with certainty. If Meissner's theory were correct, 

 every q^^, or nearly every egg, in the lower part of the tuba 

 and in the commencement of the uterus, should contain one or 

 several oil-drops. This, however, is by no means the case. It 

 is by far the smallest number of eggs that contain such drops. 

 On the other hand, in the unimpregnated females of Ascaris 

 suilla, we could trace the formation of oil- drops in a far greater 

 proportion. Not unfrequently, individuals are met with, in the 

 uterus of which most of the eggs are furnished with one or 



Ann. ^ Mag, N. Hist. Ser. 3. Vol. i. 13 



