102 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
In order to study the eggs, it is of course necessary to dissect them 
from the mother. This, again, is a tedious and delicate process, and it 
is rarely possible to free the egg entirely from the closely applied ovi- 
duct and ovary. This fact causes excessive trouble later, since the 
fragments of oviduct and ovary attached to the egg prevent one's 
plaeing it in any desired position or rolling it about at will, under à 
cover-glass. 
For surface study of the early stages the eggs were then mounted in 
glycerine under a cover-glass supported by bits of capillary tubing thick 
enough to allow free motion to be given to the object. It was found 
impossible to use to advantage any stain for this study, because all the 
stains tried colored the cytoplasm more than the nucleus, and made the 
egg so opaque that cell boundaries and nuclei could not be distinguished. 
For the stages from one to about sixteen cells, eggs fixed in Flem- 
ming's solution are the best, as the slight darkening produced by this 
reagent is of advantage in stages where the egg is cleft into but few 
cells. For later stages this darkening is a disadvantage ; eggs killed by 
other methods, or bleached after fixing with Flemming's fluid, must be 
used. 
The eggs were moved about by rolling the cover-glass on its rollers, 
and drawings were made of different views thus obtained. It is here 
that the ovary and bits of oviduct attached to the egg cause infinite 
delay and vexation, in preventing the eggs from rolling easily or rest- 
ing in any except certain positions. The time required for the work is 
certainly doubled, perhaps more than doubled, by this. 
With early stages, camera drawings can be made at once from the egg 
after a favorable position is gained ; but after the egg has reached a 
stage of about thirty cells, it is necessary first to roll the egg and make 
many tentative free-hand drawings of the different surfaces, until 
together they show the whole surface of the egg and the relation of 
every cell to all surrounding cells. The egg is then oriented and a 
camera figure made which shows the exact form of the cells in the 
middle region of the upper surface, and the position of all the nuclei of 
that surface. The cell boundaries about the periphery corresponding 
to these nuclei are then supplied from the free-hand sketehes. "This 
method, while not giving mechanical accuracy for the form of the cells 
about the periphery of a late stage of cleavage, does permit of complete 
accuracy 80 far as the relations of cells to one another are conoerned ; 
any other method with eggs in which the cell boundaries are so 
faintly marked on the surface is impracticable. 
