418 F. M. BALFOUR. 



of about 0"06 mm. as a layer of fine granules, which stain deeply 

 with osraic acid. They are at first confined to a stratum of proto- 

 plasm slightly below the surface of the ovum, and are most 

 numerous at the pole furthest removed from the germinal vesicle. 

 They are not regularly distributed, but are aggregated in small 

 masses. They gradually grow into vesicles, in the interior of 

 which oval solid bodies are developed, which form the permanent 

 yolk-spheres. These oval bodies in the later stages exhibit a 

 remarkable segmentation into plates, which gives them a peculiar 

 appearance of transverse striation. 



Certain bodies of unknown function are occasionally met 

 with in the vitellus, of which the most remarkable are those 

 figured at x on PL XVIII, fig. 25, a. 



(8) . The germinal vesicle. — A reticulum is very conspicuous in 

 the germinal vesicle in the freshly formed ova, but becomes much 

 less so in older ova, and assumes, moreover, a granular appear- 

 ance. At first one to three nucleoli are present, but they gra- 

 dually increase in number as the germinal vesicle grows older, 

 and are frequently situated in close proximity to the membrane. 



The Mammalian Ovary (PL XIX, figs. 35 — 41). 



The literature of the mammalian ovary has been so often 

 dealt with that it may be passed over with only a few words. 

 The papers which especially call for notice are those of Pfluger,i 

 Ed. van Beneden,^ and especially Waldeyer,^ as inaugurating 

 the newer view on the nature of the ovary, and development of 

 the ova ; and of Poulis * and Kolliker^ as representing the most 

 recent utterances on the subject. There are, of course, many 

 points in these papers which are touched on in the sequel, but 

 I may more especially here call attention to the fact that I have 

 been able to confirm van Beneden's statement as to the existence 

 of polynuclear protoplasmic masses. I have found them, however, 

 bv no means universal or primitive ; and I cannot agree in a 

 general way with van Beneden's account of their occurrence. 

 I have found no trace of a germogene (Keimfache) in the sense 

 of Plliiger and Ed. van Beneden. My .own results are most in 

 accordance with those of Waldeyer, with whom I agree in the 

 fundamental propositions that both ovum and follicular epithe- 

 lium are derived from the germinal epithelium, but I cannot 



' 'Die Eierstocke d. Saugetliiere u. d. Meuschen,' Leipzig, 1863. 

 - ' Composition ct Signification de I'oeuf Acad. v. dc Eelgique,' 1868. 

 ' ' Eierstock u. Ei.' Leipzig, 1870. 



* 'Trans, of Roy. Society, Edinburgh,' vol, xxvii, 1875, and this 

 Journal, vol. xvi. 

 ' 'Verhandlung d. Phys. Med. Gesellscbaft,' Wurzburg, 1875, N. F. 



Bd. viii. 



