and Fei'tilization in the Nematoidea. 185 



at a certain spot in its periphery. This is the stage that corre- 

 sponds with Meissner's mature germ-cells. The sphere then 

 exhibits a very sharp outline^ " a well-defined margin/' as Nelson 

 says. Nevertheless Bischoff here again denies the existence of 

 a membrane, and calls the sphere a sarcode-globule. The ques- 

 tion is a difficult one to decide. We should declare ourselves 

 decidedly against the assumption of an enveloping membrane, 

 so long as the deposition of granules around the original vesicle 

 is still going on. But whether the outer layer of the spheres 

 does or does not harden into a membrane in the lower part of 

 the testis, or in the so-called ductus defer ens j it is difficult to 

 decide. We are inclined to believe that the same conditions 

 occur here as with the ova in the vitellogene, and that the sphere 

 gradually increases in density towards the periphery. 



Nelson asserts that the nuclei (the original clear vesicles) of 

 the corpuscles are persistent, so as to free themselves from their 

 granular envelope within the female genitalia, and reappear as 

 spermatic cells. This is certainly an error. The nucleus dis- 

 appears very early, and no trace of it is then to be found. 



Hitherto no further development of the seminal corpuscles in 

 the male genitalia has been observed. The following stages 

 have always been met with in the female sexual organs. We 

 have, however, been more fortunate than previous observers, 

 inasmuch as we have been able to trace the development of the 

 seminal corpuscles further in the seminal sac of Ascaris suilla. 

 After the clear globules with accumulations of granules have 

 increased by division, they reach the seminal vesicle ; they 

 may then be regarded as development-cells of the zoospermia. 

 From any point of the aggregation of granules there rises a 

 small arched process, which gradually grows up into a finger- 

 shaped body. We have not been able to observe that this pro- 

 cess carries a membrane forward with it, by which the question 

 of the presence or absence of the membrane might have been 

 solved. The sphere rather separates very soon, so that the 

 aggregation of granules with its attached finger-like body be- 

 comes free. It is not rare to meet with aggregations of granules 

 which bear from two to four finger-like bodies, although we 

 have been unable to ascertain that all these bodies originate 

 from a single cell. It is possible that such groups are produced 

 by several aggregations of granules adhering to each other, and 

 as it were becoming amalgamated. However, we have never 

 observed that the aggregations bearing several finger-like pro- 

 cesses were larger than those which were furnished with a single 

 one. Lastly, we find loose finger-like corpuscles, which are no 

 longer adherent to the granular aggregations. These have the 

 greatest resemblance to the thimble-like corpuscles, which are 



