NOTES AND MEMORANDA. 397 



the mesoblast, with which layer its earlier stages of development are 

 most intimately bound up. 



Evolution of the Male and Female Genital Glands of Mammalia. 

 — M. Ch. Eouget gives * a short account of his work on this subject, 

 from which there is so much still to be learnt that is of great import- 

 ance in any comprehensive or correct account of the structure and 

 relations of the group. 



So soon as the common rudiment of the genital glands gives rise 

 to those peritoneal cells which invest the genital layer, and these 

 cells thicken (twelfth day in the rabbit), a number of cylindrical cells 

 with large nuclei are found among them (primordial ovules) ; 

 gradually they pass inwards and become connected with the so-called 

 segmental cords, in which they form lines, the separate elements of 

 Avhich are separated from one another by masses of small cells. The 

 first sign of sexual differentiation is the disappearance of the ovules 

 of the epithelial layer, and the formation of the earliest rudiments of 

 the tunica alhuginea. From the sixteenth to the twentieth day the 

 number of ovules increases rapidly, and that the more in the male ; 

 the primitive cells, with an ovoid nucleus, form a reticulum for the 

 ovules in the female, and seem to be the rudiments of the flattened 

 cells of the primordial follicles. In the cortical portion there are 

 small cells, which increase very rapidly in the male ; the ovules 

 persist even during infancy in the male glands, and apjiear to form 

 the large cells, to which La Valette St. George has given the name of 

 spermatogonia. The important point, then, that the ovules are essential 

 elements of the testicle, which was first shown by Balbiani to be true 

 of the Plagiostomous Fishes (and more recently of a young sheep j, 

 may be fairly extended to all mammals at any rate, as M. Eouget has 

 observed them in the human embryo, in rabbits, cats, and dogs. 



Natural Science Prizes of the Brussels Academy. — The subjects 

 for the Natural Science prizes of the Brussels Academy for 1880 are 

 the following : — 



1st. (A geological subject.) 



2nd. " Explain the history of the germinative vesicle in ova 

 capable of developing by parthenogenesis," The author to choose the 

 object of his essay amongst the different sjiecies of animals in which 

 parthenogenetic development has been positively established. 



3rd. " New observations are required on the relations of the 

 pollen-tube with the ovule in one or more phanerogams." 



The value of the medals to be awarded are 800 francs each, and 

 the essays must be written in French, Flemish, or Latin. 



Cells and Nuclei. — Dr. Klein continues, in the ' Quarterly Journal 

 of Microscojjical Science,' f his observations on the structure of cells 

 and nuclei, forming Part II., and dealing with the epithelial and 

 gland-cells of mammals. This was written before the appearance of 

 Professor W. Flemming's article on the same subject in the ' Archiv 



* ' Comptes Rendus,' Ixxxviii. (1879) 602. 

 t 'Q. Jouni, Mier. Sci.,' xix. (lS7i>) 125. 



