430 
EDWIN G. CONKLIN 
3d day a gasfcrula was present, normal in form, but with the an- 
terior half yellow and the posterior half gray. On the 8th day 
this egg had given rise to a normal little snail, still unhatched; 
and on the 12th day it hatched and appeared entirely normal. 
2. Isolated in the 4-cell stage, the four cells being of a uni- 
formly yellow tint, while the gray material was contained in a 
large spehre about one-fifth the volume of the entire egg. This 
sphere had been extruded at the animal pole and was really the 
second polar body, and upon it the first polar body was attached 
(figs. 27-29). On the 2d day the blastula stage was reached it 
was of a uniformly yellow color but was otherwise quite normal. 
On the 3d day the gastrula was formed (fig. 30) which was chiefly 
yellow in color, though the ectoderm was more transparent than 
the endoderm. Daily examinations showed that the develop- 
ment of this embryo was entirely normal and on the 12th day a 
normal snail hatched from the capsule. The gray sphere (second 
polar body) took no part in this development, but died soon 
after its separation from the remainder of the egg. 
3. An egg exactly similar to the preceding, gave rise on the 
2d day to a large number of blastomeres which were loosely united, 
and which did not develop further, though observed up to the 
8th day. The gray sphere never divided and took no part in the 
development. 
4. An egg similar to (2) was isolated in the 4-cell stage. The 
gray sphere (second polar body) in this case was very large, com- 
prising almost one-half the volume of the entire egg. On the 
2d day the gray sphere appeared to be composed of many small 
spherules, but with outlines so obscure that it was difficult to see 
them at all; after the 2d day no further development of the gray 
sphere occurred. On the 3d day the yellow part of the egg had 
given rise to a gastrula, yellow in color but with ectoderm more 
transparent than the endoderm. Subsequent daily examinations 
showed that the development of this embryo was entirely normal, 
except for size and color, until on the 12th day a normal little 
. snail hatched and lived for many days. 
Experiment 7. Lymnaea eggs after both maturation divisions 
and 1 hr. before the first cleavage were centrifuged 20 min. full 
