STUDIES IN THE EXEEK LM ENTA li ANAT.YSIS OF SEX. 271 
It must be remarked tliat in the crustacean ovary there are 
no nurse-cells which elaborate the yolk and pass it on to the 
(\i’‘gs ; the latter, on the contrary, are bathed in the blood and 
take up the fat directly fro!u it. 
The Weigert method ot‘ staining the eggs did not shed any 
important additional light on the nature of the yolk-globules. 
After treatment with the bichromate for eighteen hours, the 
yolk-globules were intensely stained with the heemotoxylin 
after treatment with potassium ferri cyanide. It can only be 
said that the yolk-globules are acted on by the bichromate 
more rapidly than the neutral fat-globules in the liver. 
The treatment of frozen sections of crab’s liver and of 
sacculina roots with Nile Blue gives very clear pictures of the 
abundant presence of fat in the liver-cells and in the cells 
of the Sacculina roots. The cytoplasm and nuclei of the 
cells in both cases stain blue, while the large neutral fat- 
droplets in the liver-cells are picked out in brilliant red, and 
the smaller fat-droplets in the Sacculina roots are stained 
with a magenta tinge. The slight difference in the red 
colour of the liver fat and of the Sacculina fat probably 
indicates a slight difference in chemical composition between 
them, but it is not nearly so marked as the difference between 
the neutral fat of the liver and the yolk-globules of the 
mature ova. The Weigert method also indicates a very 
slight difference in the composition of the fat of the two 
cases, since the Sacculina fat-droplets are slightly more 
rapidly acted on by the bichromate than is the case with the 
liver fat. The difference is, however, so slight that it may 
merely be due to the smaller size of the fat-globules in the 
Sacculina roots. 
It is possible, therefore, to show , by conclusive micro- 
chemical tests that the Sacculina roots take up fatty material 
from the blood of the host, which is laid down at first princi- 
pally, at any rate, as neutral fat. Now, we have seen that 
the ova in the course of their growth take up fat from the 
blood in the form of neutral fat, so that the statement made 
in previous studies that the Sacculina roots are abstracting a 
