200 OVARY AND PAROVARIUM, BY W. WALDEYER. 



of ova occurs at a later period, we have in these structures one 

 of the most remarkable examples known of persistence of life 

 in an elementary organism, lasting in Man for at least forty 

 years. 



The secondary growths of the primordial egg cells, forming 

 the secondary yolk and the zona pellucida, have now been 

 demonstrated to be the products of the follicular epithelium. 

 Hence it is only the primordial egg that can be regarded as a 

 simple cell, all mature ovarian ova being already compound 

 structures. 



This proposition is apparently in contradiction to the fact that the 

 ova of Mammals and of Batrachia, as well as those of many lower 

 animals, undergo fission with all their constituent parts. The contra- 

 diction, however, is not so complete and thorough as it appears to be. 

 On the one hand it may be asked whether, in consequence of the 

 genetic connection between the ova and the follicular epithelium, the 

 products of the latter, when they are present in small quantities, 

 cannot be completely assimilated to the original egg cells ; on the 

 other hand it is very doubtful whether, in the above-named classes, 

 all the materials composing the ova can be applied directly to the 

 construction of the embryonic body. At all events, Gotte (47) has 

 shown, in regard to the Batrachia, that the so-called " gland germ " of 

 Kemak, that is considered to be a product of fission, serves for the 

 most part as aliment for the larva. Further and more exact re- 

 searches in regard to the process of its fission and the behaviour of 

 its products to the cells are still required. 



There certainly appear to be eggs that possess no secondary yolk ; 

 for, independently of the ova of the Protozoa, respecting which no 

 opinion can be formed at present, Ganin (41) has recently found in 

 the section Pteromalina of the Hymenoptera mature ova in which there 

 were no yolk granules, and the germinal vesicles of which were only 

 surrounded by a small quantity of transparent protoplasm. 



The resemblance of the ova of the several classes is obvious 

 from the preceding observations. The primordial ova are 

 everywhere identical ; and the ripe ovarian ova of all Verte- 

 brata are strictly comparable with each other, since they are 

 all composed of the primordial ovum and other material pro- 

 ceeding after the same fashion from the follicular epithelium. 



