STUDIES ON GERM CELLS 389 



and most successful methods for studying the Keimbahn are 

 fixmg in Gilson and staining in Mayer's acid hemalum followed 

 by Bordeau-x red. Entire larvae may be fixed, sectioned and 

 stained in this way. To bring out cytoplasmic details other 

 methods were resorted to. The anterior and posterior ends of 

 larvae were cut off and the middle part of the body containing 

 the ovaries, and eggs and young were fixed in Meves' fluid. In 

 other cases the eggs and young were dissected out and fixed in 

 Meves' fluid. Still other larvae were fixed in Carnoy's solution. 

 The best fixation was obtained with Gilson's Mercuro-nitric 

 fluid. Besides acid hemalum the following stains were used: 

 Heidenhain's iron hematoxylin followed by Bordeaux red or 

 eosin, the iron hematoxylin method used by Rubaschkin ('12) 

 in his studies of the mitochondria in the embryonic cells of the 

 guinea pig, safranin followed by light green, Altmann's acid 

 fuchsin differentiated in picric acid, Benda's method for the study 

 of mitochondria, and the Erhlich-Biondi triple stain. 



The morphological continuity of the germ cells. The ovaries 

 of Miastor lie on either side of the body in the tenth or eleventh 

 segment. They appear yellowish green in living white larvae, 

 but are whitish transparent in the young yellowish larvae. 

 Each ovary, when in the stage shown in figure 27, is surrounded 

 by a thin cellular envelope (en) and contains typically thirty- 

 two oocytes (ooc.n) each with an accompanying group of meso- 

 dermal nurse cells (n.c), which are enclosed with it in the follic- 

 ular epithelium (f.ep). The oocytes grow at the expense of the 

 nurse cells, separate from the ovary, and are distributed through- 

 out the body of the larva. Usually from five to seventeen em- 

 bryos develop in one larva, but sometimes only one or two larvae 

 are produced by a single mother-larva. 



The nucleus of the oocyte (fig. 27, ooc.n) is large and clear, 

 and the chromatin within it forms slender threads, rather evenly 

 scattered about in the nuclear sap. 



Figure 28 is a longitudinal section of an oocyte just before 

 the maturation division. The germinal vesicle (g.v.) is large and 

 clear and contains a great number of small scattered chromatin 

 granules. It lies near one side of the oocyte in preparation for 



