GOLGI BODIES, ETC. 



327 



careful study of the origin and morphology of any doubtful cell 

 body, will, however, provide reliable evidence for identification. 

 Another warning must be given — never try to ascertain the nature 

 of granules in developing eggs without first studying the oogenesis 

 of the animal in question. Eggs after spawning or laying are 

 difficult objects to study by these methods, and even the most 

 experienced worker is imable to give an interpretation until he 

 has worked at the oogenesis. It should also be remembered that 

 there are periods in the development of the cell during which the 

 mitochondria are often able to resist becoming dissolved in lipoid 

 solvents ; these periods are in the early spermatogonium in some 

 animals, and during the last stages of spermatogenesis (sperma- 

 teleosis) in all animals, and sometimes in large oocytes. See also 

 the work of Regaud, Arch. (TAnat. micr., xi. 



N^oia Bene. With regard to the oil used for clearing and 

 imbedding, it should be pointed out that all these tables are based 

 on preparations cleared and imbedded in xylol, which occasionally 

 tends to extract lightly osmicated fat. Vegetable oils like cedar 

 wood oil seem to be less active in this way. We have rarely * 

 found that chrome-osmicated fat, or " Kopsched " fat, is extracted 

 either by xylol or xylol-balsam. See also § 651. 



735. Differentiation between Mitochondria and Fat (Olein, 

 Stearin and Palmitin Mixtures especially). 



* Thi.s certainly happens in the case of the delicate fat vacuoles of 

 tissue -cultured fibroblasts, see § 691. 



