CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 449 
The Fixing and Staining Reactions oe the Cell Elements 
of Spermatocyte and Spermatid. 
In table form I have set out on p. 448 the reactions of 
the nucleus, centrosomes, mitochondria (macromitosome), 
micromitosome, and acrosome to the various fixatives. Iron 
haematoxylin and some other stains were used to judge 
staining power, any staining method serving to standardise 
a number of fixing methods. 1 
These results are mainly derived from Pieris, Smerinthus, 
Porthesia, and Vanessa. A compromise between Fixatives 1 
and 2 can be got by using reduced acetic acid, but as 
Champy has insisted the use of acetic is not really indicated, 
and constantly leads to faulty results. The micromitosome 
in some forms seems to be more affected than in others, 
and I am inclined to believe that this body is somewhat 
different in different species. In Porthesia I believe the 
micromitosome is constantly present, but as my material 
was all fixed in Flemming, the body was very vague and 
lightly staining. The Regaud reaction is a very useful 
one, for from it we know that the acroblasts are in some 
way different from the mitochondria. This applies also to 
the centrosome ; the whole table of reactions shows that 
the acetic acid favours nucleus, centrosome, and aster. The 
mitochondria are different in this way, and again the 
acroblasts are more delicate than the mitochondria. I 
believe that acetic acid should never be used unless for 
very special purposes. A great deal of the work at present 
done on chromosomes is carried out with acetic fixatives; 
these are unnecessary and probably destroy many features 
of interest in the cytoplasm. Of course, in the cases where 
chromosomes are very small acetic acid is an advantage for 
it gives a sharp stain. A curious effect of Champy is 
sometimes to cause the nucleolus to stain very black and 
1 The time given to washing out of the material after removal from 
the fixative is an important factor in staining. 
