292 ANIMAL PARASITES. 



extreme portion of the ovary, formed only of a tunica propria 

 without an epithelial coat. It is analogous to the germ-partition 

 (Keimpach) of the insects, generally smooth on the outside, some- 

 times constricted at its anterior open end by a sort of delicate 

 sphincter (for example, in the Mermites, which are nearly allied to 

 the Nematoida), and dilated in the middle. In this, again, are 

 found the female germ-cells, cells circumscribed by the most deli- 

 cate lines, exactly analogous to the male germ-cells, and with a 

 vesicular nucleus and nucleolar corpuscles (see these structures 

 further on). The nucleus divide? into daughter- nuclei (nucleolar 

 vesicles), and these again into 8, 10, or more nuclei (new nucleolar 

 vesicles), which, becoming affixed to the walls, each push out the 

 walls of the germ-cell individually. These projections constantly 

 become more independent, and grow into daughter-cells, which 

 represent the young ova with their nuclei, daughter-nuclei, and 

 germinal vesicles in which the germinal spot is afterwards 

 developed, but always remain in open communication with the 

 mother-cell until the maturity of the contents, the yelk ; they 

 then become pyriform and provided with a stem, which, forming 

 an open canal, connects the lateral cells with the mother-cell. 

 As soon as they begin to fill with yelk, they are called egg- 

 racemes (Eiertrauberi). 



According to this view of Meissner, therefore, the germinal 

 vesicles are formed several together, in separate mother-cells 

 by endogenous increase. At the same time the mother-cells 

 become converted, by a sort of bud-formation, into a group 

 of smaller cells, each of which possesses a germinal vesicle and a 

 separate membrane (a rudimentary egg). These young are also 

 united by a peduncle to the remains of the original mother-cell ; 

 but the remains of the mother-vesicle, always lying in the centre 

 of the ovigerous canal, as in the Gordiacei and also in the Asca- 

 rides, form a central axis, which is often very distinct (but some- 

 times indistinct), and around which the ova themselves are 

 arranged like radii. 



Neither Bischoff, nor Nelson, nor Thompson, can coincide with 

 this view, and Thompson especially objects, certainly not unjustly, 

 that Meissner has been too quick in extending his observations 

 on the Gordiacei to the other nematode worms. The above- 

 mentioned observers never found a union of the eggs in groups, 

 for example in Ascaris mystax. The germinal vesicles were 

 always free in a granular fluid, which gradually collected round 



