THE MICROCOSM OF THE EGG 141 
Another kind of experiment shows that a half or 
less may be as good as a whole. By delicate meth- 
ods of microscopic vivisection, Professor Delage 
was able to cut off non-nucleated fragments from 
a sea-urchin ovum. They accepted fertilization, 
however, and developed into embryos. In many 
cases, when a fertilized egg-cell has divided into two 
cells, these can be shaken apart with the result 
that each develops into an entire animal. If in the 
two-cell stage of the developing frog ovum, one cell 
be punctured with a heated electric needle, the 
remaining cell will develop into a one-sided hemi- 
embryo or into a half-sized whole embryo, accord- 
ing as the punctured ovum is kept fixed or allowed 
to move (and readjust itself) in the water. Indeed, 
if a part of an ovum or of a developing ovum is to 
serve as the equivalent of a whole, the essential 
condition seems to be a restoration of the typical 
topography and a re-establishment of the pro- 
portions of materials. Ifa vessel of sea-water con- 
taining developing eggs of the lancelet be shaken 
at the two-cell stage, the. result, according to the 
amount of shaking, will be a double supply of dwarf 
embryos, or a set of Siamese twins. Even at the 
four-cell stage, the shaking will result in numerous 
dwarf embryos, or in queer Siamese triplets and 
quadruplets. Perhaps, however, we have said 
enough to suggest the wonder of the egg-cell, and to 
make this certainty clear, that no easy-going view 
of the microcosm is in the direction of the truth. 
