ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 479 



as it increases in size, there appear the limiting membrane and the 

 internal plexus. 



At a later stage of development, when there has been multiplica- 

 tion of the cells, these become smaller and smaller, and the asters 

 gradually become quite indistinct. In the earliest stages of segmen- 

 tation the process of division is more difficult to follow, owing to the 

 large size and very granular contents of the cells ; on the first and 

 second day the cells become so uniformly tinted that the nuclei are 

 with difficulty made out. As the cells diminish in size the action of 

 the colouring matter becomes more and more confined to the nucleus, 

 and the author is of opinion that the chromatin of Flemming is at 

 first uniformly distributed through the cell, and that it gradually 

 separates to form a constituent of the nucleus. 



Genesis of the Egg in Triton.*— Mr. T. Iwakawa records the 

 result of observations on the genesis of the egg of the common Triton 

 (T. pyrrhogaster Boje), in which he describes the manner of depositing 

 the egg (the female turning upside down so as to place it under the 

 leaf or stem), the structure of the ovary, origin of the ovum and 

 Waldeyer's " epithelial islands " (the author's view being that the 

 ovum does have an epithelial origin), the formation of yolk- 

 spherules, the vitelline membrane, the germinal vesicle, and the " yolk- 

 nucleus." 



Formation of Fibrine.f — In 1879 Dr. Noma described the 

 alleged discovery of a third corpuscular element in blood in the form 

 of colourless disks, which he considered to be an earlier stage of the 

 red corpuscles. J This was criticised by Mrs. Ernest Hart in the fol- 

 lowing year, § her view being that they were red corpuscles that had 

 undergone post-mortem changes prior to taking part in the formation 

 of fibrine. 



Continuing her investigations and repeating the experiment of 

 " isolation " || a great number of times, she began to observe that the 

 appearances changed according to the length of time which elapsed 

 between the spreading of the layer of blood between the two glass 

 surfaces and the moment when the cover-glass was raised, and thus 

 discovered that a whole series of phenomena could be traced, leading 

 from the pale or colourless corpuscle up to the complete formation of 

 networks or bands of fibrine. In developing this method of working 

 it was found that the staining reagents recommended by Dr. Norris 

 were not sufficiently powerful to bring out all the details that could 

 be observed on the glass surfaces, and after many trials a highly con- 

 centrated solution of nitrate of rosanilin in absolute alcohol was found 

 to be the best staining reagent. The method adopted was to detach 

 the cover-glass from the slide after the corpuscles had been fixed by 

 osmic acid vapour, and to examine both the surfaces of the cover-glass 

 and the slide, to see which presented the most perfect preparations. 



* Quart. Journ. Micr. Sci., xxii. (18S2) pp. 260-77. 



t Ibid., pp. 255-9 (1 pi.). 



j See this Journal, iii. (1881) pp. 229-32. § Loc. cit. 



|| See description, loc. cit. 



