DEVELOPMENT OF THE GENERATIVE ORGANS. 711 
they are found in the oviduct shows that they have been passed 
back into the oviduct, instead of having been deposited. It 
may also be objected that the development of my germ ova 
within the epithelial cells of the parovarium is not consistent 
with the view that they are really germ ova. Brandt [830, 
Fig. 128], however, gives a remarkable figure of the young 
ovary of the Amphibian Pelobates fuscus, which presents the 
same appearance as a section of the parovarium of the 
Blow-fly. He says it is a tolerably thin section of the ovary, 
and that ‘it consists of an oval ring, smooth externally, bounded 
by a flattened epithelium, which is tuberculated internally by 
the projecting ova.’ Inthe figure there is no question as to the 
position of the ova; they are clearly represented in the interior 
of the epithelial cells. 
In concluding this section I would again draw attention 
to the fact that the original structure of the genital cord and 
the ovary are identical, so that the parovarium is merely a 
differentiated portion of the ovary, one portion of which be- 
comes a vitellogenous gland and the other a germ-gland. 
h. On the Changes which occur in the Germinal Vesicle and Free 
Nuclear Formation. 
It was formerly believed that the germinal vesicle disap- 
pears either before or immediately after fertilisation. Milne 
Edwards [861], expressing the opinion of the majority of his 
contemporaries, said: ‘The disappearance of the germinal 
vesical is a consequence of its natural death,’ and Leuckart* 
expressed the same idea in different words; he regarded the 
germinal vesicle as ‘ Concerned in the elaboration of the ovum, 
but not in the development of the embryo.’ 
Johannes Miiller [859], in 1852, declared that the germinal 
vesicle does not disappear in the egg of Entoconcha mirabilis, 
but that it divides and produces the first pair of segmentation 
* R. Wagner's ‘Handworterbuch der Physiologie,’ art. ‘Zeugung,’ by 
Leuckart. 
