PLATE 4 



EXPLANATION OF FIGURES 



Interstitial cell types from the testis of Necturus. All figures in this plate 

 were outlined with the camera lucida; magnification, 750 diameters. All are 

 taken from preparations fixed in Bensley's fluid (osmic-dichromate-acetic) and 

 stained with acid fuchsin and methyl green. Lipoid droplets appear black, 

 mitochondria and fuchsinophile granules red, nuclei green. 



25 Stromal-cell type seen during the summer months between lobules of 

 spermatogonia or spermatocytes. The nuclei may be even more flattened, as is 

 shown in figures 8 and 9. 



26 Cells surrounding partially emptied lobules in the caudal end of the testis 

 in early October. Numerous mitochondria have now appeared; no cell bound- 

 aries are as yet distinguishable. At the upper right is a connective-tissue cell 

 which has not begun transformation to an interstitial-cell type. 



27 One of the mitotic figures so numerous in early October among developing 

 interstitial cells. Among the red granules are a few of larger size than those 

 shown in figure 26. 



28 Cell in a more advanced stage of development than are those shown in 

 figures 26 and 27. The nucleus is more rounded, cell boundaries are distinct 

 and many fuchsinophile granules are decidedly larger than the granules (mito- 

 chondria?) in figure 26. 



29 Cell from the caudal end of the testis in late October. Lipoids blackening 

 with osmic acid have appeared, many of them of the same size as the fuchsin- 

 ophile granules. Nuclei are now approximately spherical and cell boundaries 

 are distinct. 



30 Cell from the same section as figure 29, but showing the idiozome, sur- 

 rounded by numerous fuchsinophile granules and blackened lipoid droplets. 



31 Cell from the caudal portion of the testis in April, showing giant centro- 

 sphere with idiozome and centrioles. Interstitial cells of this type predominate 

 in the early spring. 



32 Degenerating cell lying adjacent to the cell shown in figure 31. Cells of 

 this type are comparatively few in number in the earlier part of the spring. 



33 Degenerating cell (or cell mass?) common in the testis in May. The 

 bodies at the right are apparently masses of cytoplasm containing small fuchs- 

 inophile granules (mitochondria?). It is suggested that these may give rise to 

 such solidly staining fuchsinophile masses as the one at the left. 



34 to 39 Cell types seen in the testis in June and July. Occasionally cells 

 of the type of 35 or 36 may persist through the summer, but in the majority of 

 the animals examined their disappearance is complete. Figures 38 and 39 show 

 colls of a tyjie frequently encountered at the periphery of the testis at the time 

 the larger cells are becoming few in number. 



278 



