( 400 ) 

 EECORD 



OF CURRENT RESEARCHES RELATING TO 



INVEETEBEATA, CEYPTOGAMIA, MICEOSCOPY, &c.* 



ZOOLOGY. 



A. GENEBAL, including Embryology and Histology 

 of the Vertebrata. 



Formation of Ova and Ovaries.t — M. Cadiat is not satisfied with 

 the view generally held that the ova are formed before the ovary, and 

 that the germinal epithelium is the direct originator of the former. 

 His observations have led him to the conclusion that the germinal 

 epithelium and the ovary itself do not contain true ova until 

 an advanced period of development is reached, and till the time 

 when external characters indicate that the sex of the individual is 

 distinctly differentiated. He also finds that the epithelium of the 

 Graafian vesicle is not derived from the germinal epithelium. The 

 ovary and the Graafian vesicles are, in fact, derived from elements 

 which, even at the fourth or fifth day of the incubation of the chick, 

 may be recognized in the midst of the cells of the germinal epithelium : 

 they very soon become provided with a distinct and thick wall, which 

 plays an important part hereafter. The cellular body is highly gra- 

 nular, and though there is no distinct nucleus, there are one or two 

 large nucleoli — this is the ovoblast. At first the ovoblasts increase 

 in size and acquire nuclei and nucleoli ; they then divide, and, later 

 on, in the embryo of the sheep, it is possible to see gemmgeform bodies, 

 somewhat similar to the directive corpuscles of the ovum ; an envelope 

 of epithelial cells is gradually formed, which isolates the primitive 

 body from the neighbouring cells. Later on, the ovoblasts, or the 

 greater number of them, are converted into Graafian vesicles. At the 

 period when the follicular epithelium is developed, the central cells 

 become provided with a large slightly transparent nucleus, and we 

 soon see all the characters of the true ovum, with the exception of the 

 vitelline membrane ; this, then, has no relation to the primitive wall of 

 the ovoblast. 



Destruction of Ova and Spermatozoa. :{; — Professor Schneider has 

 observed, in the testes and ovaries of Nephelis, Aulostomum, and Hirndo, 

 cells which exhibit slow amoeboid movements ; resembling at first, 

 and in their natural position, stellate connective-tissue cells, they 

 become, under the influence of dilute acetic acid, rounded, and, save 



* [^> It should be understood that the Society do not hold themselves respon- 

 sible for the views of the authors of the papers, &c., referred to, nor for the manner 

 in which those views may be expressed, the object of the Kecord being to present 

 a summary of the papers as actualli/ published. Objections and corrections should 

 therefore, for the most part, be addressed to the authors. 



+ ' Comptes Rendus,' xc. (18S0) p. 371. 



X 'Zool. Anzeiger,' iii. (18S0) p. I'.). 



