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Nachdruck verboten. 
Closure of Blastopore in the normally placed Frog Egg. 
By H. V. Wiııson. 
About a year ago I described (Anat. Anz., Bd. XVIII, No. 9/10) 
certain cell movements occurring during the closure of the blastopore 
in the frog egg, when the egg was compressed and inverted. While 
there was every reason to believe that the movements were those 
which occurred in the normally placed egg, it seemed desirable to 
learn positively whether this was the case. For this purpose I made 
use during the past spring of the inverted microscope referred to in 
my previous communication. 
The particular instrument used by me is made by the Bausch 
and Lomb Optical Co., Rochester N. Y. The stage is horizontal, with 
the objective below it. By means of a prism placed below the ob- 
jective, the light rays are given an upward direction, passing along 
the tube which stands at an angle of about 45° to the vertical. In 
the stock pattern the aperture in the stage is too small, the stage it- 
self interfering with the light, which is necessarily placed at a lower 
level. For use the microscope was elevated on a stand above the 
level of the table, while a lamp and large bulls-eye lens were placed 
in the proper positions on the table. During the day the room was 
