THE PINEAL BODY OF THE SHEEP 263 



They vary in color from a light yellowish or greenish brown to a 

 deeper brown or even black. Occasional rod and ring forms ap- 

 pear. The larger granules are the darkest. The smaller have a 

 metallic luster. When abundant, as in the corpora pinealia of 

 half-term sheep, they give a grayish or black color to that body. 

 Their color is deepened by osmic acid, and the various haematoxy- 

 lin stains, indicating a partial lipoid nature. They are distinctly 

 cytoplasmic (i.e., extra-nuclear). In no case can similar granules 

 be seen within the nucleus. The latter, in unstained prepara- 

 tions, appears homogeneous; in stained preparations the numerous 

 chromatic granules of the nuclear reticulum simulate these black 

 cytoplasmic granules. I can find absolutely no cytologic evidence 

 for other secretory products to which, according to Galeotti, 

 the nucleus and nucleolus contribute. Nor is there any evidence 

 for a transit of melanic granules from nucleus to cytoplasm. 

 Since stained preparations reveal no cytological features (gran- 

 ules) not conspicuous in unstained sections, I cannot accept the 

 view that such are present in the sheep 



The nucleus contains only chromatic granules; the cytoplasm 

 only melanic granules. Perhaps the granules illustrated and 

 described by Dimitrova for Bos taurus, and the granules desig- 

 nated by Galeotti ('96), are of the same nature as those here 

 described for the sheep. Morphologically they appear identical. 

 Dimitrova's illustration of a pineal cyst in Bos taurus, lined with 

 irregular cylindrical cells with a few spherical granules distally, 

 can be paralleled by innumerable examples from my specimens 

 from the sheep (fig. 6 and 7), in which latter case the granules 

 are undoubtedly melanic. None of the three interpretations sug- 

 gested by Dimitrova (i.e., secretion, degeneration or mitochon- 

 drial granules) seems to accord with the facts. They cannot be 

 seen building the neuroglia fibers, hence most probably they are 

 not mitochondrial. Moreover they are absent in the cells of the 

 pineal body of the opossum where very coarse neuroglia fibers 

 appear. Nor have they been described in the histogenetic proc- 

 ess of neuroglia formation in the neural tube, where Hardesty 

 ('02 and '04) regards neuroglia, in elephant and pig, as differen- 

 tiated spongioplasmic fibers. Since they are more abundant in the 



