ZOOLOGY AND BOTANY. MICROSCOPY, ETC. 565 



or plasmodial ova, which are suflSciently common in the former, are much 

 more rare than the ordinary unicellular ova. Mr. Beddard points out 

 that the fact of there being two kinds of ova with a different mode of 

 development is not new to the Vertebrata, as the " egg-nests " of Elasmo- 

 branchs suffice to show ; and these egg-nests are common among Vertebrates. 

 In all these, however, both kinds of eggs have morphologically the value 

 of a single cell. The important facts to be borne in mind in comparing the 

 egg-nests of Elasmobranchs with the ova of Dipnoi appear to be the early 

 formation of the complicated follicular layers in the latter and the early 

 commencement of yolk-secretion ; the temporary fusion of the primitive 

 ova in the Elasmobranchii, and the degeneration of some of them becomes 

 permanent in the Dipnoi, the ovum being the equivalent of a whole nest. 

 The apparent absence of any protoplasm in the yolk-mass of these remark- 

 able structures in the Dipnoi renders it extremely unlikely that the structure 

 developes into an embryo. The formation of ova as described by Prof. 

 Huxley in Lacinularia appears to be clearly analogous to the fusion of a 

 number of germinal cells in Protopterus and Ceratodus. 



Vesicle of Balbiani.* — M. L. F. Henneguy has been studying sections 

 of ovaries of young guinea-pigs and rats, fixed immediately after death by 

 riemming's mixture of chromic, acetic, and osmic acids ; in the young ovules 

 he always found a slightly refractive body with well-marked contours, placed 

 near the germinal vesicle. This — the vesicle of Balbiani — is found in young 

 primordial ova, but is not found in such as are more advanced ; its colora- 

 tion is uniform, its substance chromatophilous, and not arranged in a 

 plexus as in the nuclei. The author enumerates the various forms in 

 which he has succeeded in finding it, and then passes to the very interesting 

 observation that his studies on the testicle of the rat has shown him that 

 the so-called accessory nucleus which has been recently studied by Nuss- 

 baum and Platner, ought to be regarded as comparable to the vesicle of 

 Balbiani in ova. 



The only reagent which, at present, is found to be useful in fixing this 

 vesicle is that of Flemming. 



Atavism.t — Mr. J. Bland Sutton tries to show that, using the classi- 

 fication of Prof. Gegenbaur, all examples of atavism are palaeogenetic, and 

 that none are neogenetic, or not found as a germ in the embryo ; the prostate 

 is selected as affording a remarkable instance of atavism, and it is regarded 

 by Mr. Sutton as a suppressed uterus, the fibro-muscular tissue representing 

 the matricial walls, the follicles corresponding to the reticular glands, and 

 the reticulus itself being identical with the cervix uteri and the immediate 

 adjacent portion of the vagina. It seems to be clear that the prostatic 

 concretions and egg-shells agree structurally and chemically and are pro- 

 duced by homologous organs, so that man has in his prostate an unimpeach- 

 able witness of an ancestry with the feathered tribes low down among the 

 oviparous reptiles. 



Dealing with secondary sexual characters, the author urges that the 

 known facts seem to point to the conclusion that the epiblast is chiefly 

 derived from the male element, while the female pronucleus is chiefly re- 

 sponsible for the hypo- and greater portion of the mesoblast ; if this be 

 true, the transmission of characters peculiar to the male is not so obscure as 

 many have supposed. 



* Sep. Eep. Bull. Soc. Philomath. Paris, 1S87, 4 pp. 

 t Proc. Zool. Soc. Lond., 1886 (1SS7) pp. 551-8. 



