No. 3.] ALLOLOBOPHORA FOETIDA. 491 
eggs, it is necessary to draw only one egg at a time into the 
pipette, and for this purpose it is advisable to make extremely 
small pipettes. Those that have proved the most serviceable 
have a final aperture of two-thirds of a mm. and are 6 cm. in 
length. The advantage of the latter is that it allows the hand 
to rest on the stage of the dissecting microscope. 
The fixative recommended by Vejdovsky (19), chromo-acetic, 
has proved the best for whole mounts, and allows the entire 
egg to be studied under a very high magnification. Alum 
cochineal has proved the most satisfactory stain for these 
whole mounts. 
In order to study these eggs with a Zeiss 2 mm. immer., it 
is necessary to mount them with great care, as this lens has a 
working distance of about .2 mm. and many of these eggs 
measure .15 mm. I found it necessary to make glass feet by 
cutting square cover glasses of the proper thickness into nar- 
row strips, about 15 mm. X 3 mm. It is safer to use four 
of these, inserting half their length under the cover, in order 
to be able to push it in any direction a sufficient distance com- 
pletely to revolve the eggs. It is essential to ascertain the 
diameter of the egg, the thickness of each foot, and the thick- 
ness of the cover glass. A working distance of .23 mm. can 
safely be allowed, as it is not essential to focus entirely through 
an egg. Ifa first cleavage stage measures .16 mm. one can 
safely use feet measuring .17 mm. and a cover.06 mm. These 
very thin covers can be obtained only by special order. The 
feet are now in the market ; but as their thickness is variable, 
it is not safe to use them without remeasurement. They can, 
however, be cut in the laboratory as quickly as those of card- 
board. This method is given in detail to avert any blunder 
similar to one made by myself. In the fall of 1893 I was 
obliged to remount all the material collected the previous sum- 
mer, as the mounts were made with the regulation paper feet. 
It was only after much experimenting with both feet and cov- 
ers, that the above method was reached. Thin layers of isin- 
glass were first utilized as covers, but they have too much 
spring to admit of being safely pushed over the feet, and are 
thus apt to crush the eggs. Any number of eggs can be 
