176 THE GERM-CELLS 



gland of this animal be treated with a mixture of saffranin and methyl- 

 green, the egg-nuclei are coloured red, the sperm-nuclei bluish green. 

 A similar difference was afterward observed by Auerbach ('91) in 

 the case of many vertebrate germ-cells, where the egg-nucleus was 

 shown to have a special affinity for various red and yellow dyes 

 (eosin, fuchsin, aurantia, carmine), while the sperm-nuclei were espe- 

 cially stained with blue and green dyes (methyl-green, aniline-blue, 

 haematoxylin). He was thus led to regard the chromatin of the ^g^ 

 as especially " erythrophilous," and that of the sperm as " cyanophi- 

 lous." That the distinction as regards colour is of no value has been 

 shown by Zacharias, Heidenhain, and others ; for staining-agents can- 

 not be logically classed according to colour, but according to their 

 chemical composition ; and a red dye, such as saffranin, may in a 

 given cell show the same affinity for the chromatin as a green or blue 

 dye of different chemical nature, such as methyl-green or haema- 

 toxylin. Thus Field has shown that the sperm-nucleus of Asterias 

 may be stained green (methyl-green), blue (haematoxylin, gentian 

 violet), red (saffranin), or yellow (iodine), and it is here a manifest 

 absurdity to speak of " cyanophilous " chromatin (r/". p. 335). It is 

 certainly a very interesting fact that a difference of staining-reaction 

 exists between the two sexes, as indicating a corresponding difference 

 of chemical composition in the chromatin ; but even this has been 

 shown to be of a transitory character, for the staining-reactions of the 

 germ-nuclei vary at different periods and are exactly alike at the time 

 of their union in fertilization. Thus Hermann has shown that when 

 the spermatids and immature spermatozoa of the salamander are 

 treated with saffranin (red) and gentian violet (blue),^ the chromatic 

 network is stained blue, the nucleoli and the middle-piece red ; while 

 in the mature spermatozoon the reverse effect is produced, the nuclei 

 being clear red, the middle-piece blue. A similar change of staining- 

 capacity occurs in the mammals. The great changes in the staining- 

 capacity of the egg-nucleus at different periods of its history are de- 

 scribed at pages 338-340. Again, Watase has observed in the newt 

 that the germ-nuclei, which stain differently throughout the whole 

 period of their maturation, and even during the earlier phases of 

 fertilization, become more and more alike in the later phases, and at 

 the time of their union show identical staining-reactions.^ A very 

 similar series of facts has been observed in the germ-nuclei of plants 

 by Strasburger (p. 220). These and many other facts of like import 

 demonstrate that the chemical differences between the germ-nuclei 

 are not of a fundamental but only of a secondary character. They 

 are doubtless connected with the very different character of the meta- 

 bolic processes that occur in the history of the two germ-cells ; and 



1 By Flemming's triple method. ^ '^2, p. 492. 



