90 CARNEGIE INSTITUTION OF WASHINGTON. 



and stored and to which it is constantly adding albuminous and other 

 submicrons derived from the surrounding tissue fluids, where they exist 

 in the colloidal state. 



An interesting reaction of peritoneal mesothelium to granular sus- 

 pensions and laked blood has been demonstrated by Dr. R. S. Cunning- 

 ham. Using cats for his experiments, he finds that these mesothelial 

 cells show a great phagocytic activity towards injected suspensions of 

 carbon and carmin, and where the injections are repeated for a period 

 of several days the cells change from the characteristic flattened pave- 

 ment type to the cuboidal form with large oval nuclei and an increased 

 amount of cytoplasm. The enlarged cells continue to phagocytize 

 the injected material. Where laked heterogeneous blood is used, the 

 reaction is even more striking, the cells rounding up as if preparing 

 to separate from the tissue to which they are attached. 



Tissue cultures of embryonic chick liver have been made by Dr. 

 Ruth S. Lynch. The best results were obtained from 8-day chick 

 embryos. The liver cells migrate out from the explant in the form 

 of a membrane, the maximum outgrowth being usually reached at 

 48 hours. Degeneration changes begin to appear in about 72 hours, 

 and it is interesting to note that the degenerating cells do not show 

 centrospheres, which are so characteristic in mesenchyme cells. 



A cytological study of sympathetic nerve fibers in the chick has been 

 made by Dr. Matsumoto, who found that with the aid of vital dyes the 

 structure and distribution of mitochondria, granules, and vacuoles 

 could be demonstrated in fibers cultivated in vitro. Neutral red was 

 used for the granules and vacuoles, and Janus black No. 2 for the mito- 

 chondria. It was found that these dyes gave excellent results when 

 used separately and also when made up together in the same solution. 



A preliminary communication has been made by Mr. D. T. Smith 

 regarding the formation of melanin pigment in the retina of the chick. 

 The morphology of melanin granules in the eye v/as studied in a series 

 of chicks ranging from 42 hours to 17 days of incubation. "V\Tien grown 

 in cultures it was found that these granules could be clearly distin- 

 guished from mitochondria, differing in their staining reaction and their 

 movement within the cytoplasm of the cell. No evidence was obtained 

 to show that they were developed from mitochondria, nor was there any 

 evidence that they were extruded from the nucleus. 



Continuing mvestigations previously made at the University of Liege, 

 on the histogenesis of the sex glands, Dr. J. Firket has studied the testes 

 of young rats and finds that the primary germ cells disappear entirely 

 between the tenth and the fifteenth day after birth. Thus the sper- 

 matogonia can be derived only from the small epithelial cells and are 

 in reality secondary germ cells. This is in contrast to the chick, where 

 at least some of the primary germ cells develop into oocytes and sper- 

 matocytes. 



