106 CARNEGIE INSTITUTION OF WASHINGTON. 



cochlear nucleus of the eighth and of the nucleus of the sixth cranial 

 nerve, whereas the cells of the vestibular nucleus of the eighth contain 

 much fewer. The quantitative variations of mitochondria in the 

 individual cells of one given nucleus are very slight. 



Pursuing his researches on the behavior of the azo dyes in the 

 body, Professor Herbert M. Evans has studied the ovary, and espe- 

 cially the atresic follicle, in their reaction towards the vital stains of the 

 azo group. He finds that the beginning of the degeneration of the 

 granulosa cells is often marked by an abnipt change in their reaction 

 toward these dyes. Normally resistant to the entry of the dye, the 

 degenerating cells may house large "droplets" of vital color, so that 

 the w^hole folhcular epithelium is finally laden with it. This reaction, 

 however, is to be separated sharply from the so-called "macrophage" 

 reaction, inasmuch as the granulosa cells that behave in this way show 

 chromatolysis and other degenerative changes, and are short-hved. 

 True macrophages play an important part in follicular atresia, and they 

 are elect ively stained by vital dyes of this class. The later stages of 

 follicular atresia are consequently marked by the presence of numerous 

 macrophages laden with the dye. The macrophages must be con- 

 sidered as utihzing the products of the disintegrating ovum towards 

 which they are attracted, and which they invade by an active penetra- 

 tion of the zona pellucida. 



Dr. Katherine J. Scott's researches on the connective- tissue cells of 

 animals stained vitally with acid azo dyes have led her to the conclusion 

 that under no conditions are the mitochondria of connective-tissue 

 cells vitally stained with these dyes. The dye granules undergo defi- 

 nite changes in accordance with the functional state of the cell, and so 

 do the mitochondria; but the respective identities of dye granules 

 and of mitochondria are always maintained. 



Starting from the relations which are known to exist between the 

 composition and concentration of the sea-water and the composition 

 and concentration of the plasma, Mrs. Margaret R. Lewis studied sea- 

 water as a medium for tissue culture. She finds that an excellent 

 medium can be made with 90 parts of sea-water (diluted to make it 

 isotonic with the plasma of the animal from which the cultures are to 

 be made) -1-10 parts of bouillon made from the muscles of the same 

 animal. It has been found that about 10 (sometmies 15 and 20) 

 parts of bouillon make the solution sufficiently hypotonic to offset any 

 evaporation which may take place, and at the same time to furnish the 

 necessary nitrogenous food for the tissue. To 100 c. c. of the above- 

 mentioned medium are added 0.02 grams of NaHCOa to neutrahze the 

 acid fonned by the culture and 0.25 grams of dextrose to supply the 

 energy for growth of the tissue. 



In vertebrates, as well as in invertebrates, several observers have 

 quite recently described amitosis followed by division of the cell and 



