786 The American Naturalist. [September, 
In our knowledge of fecondation great advance was made, 
largely by American workers. The derivation of the archo- 
plasm of the fertilized egg exclusively from the sperm was 
confirmed upon many organisms; but Wheeler found in My- 
zostoma a case of the persistence of the archoplasm of the 
ovum only. The independence of the nuclear matter derived 
from the two germ cells united in fecondation was shown by 
Riickert to be indicated in Cyclops by the bilobed condition of 
the nucleus, even to the period of formation of the germ 
layers. 
Parthenogenesis—The accepted view that the unfertilized 
hen’s egg may go through the early cleavage stages was shown 
by Barfurth and by Lau, independently, to rest upon errors in 
observation. 
Ontogenesis-—The contributions to the preformation-epigene- 
sis controversy were among the most important of the year, 
pointing to acommon ground for both sides, one, consequently, 
which probably lies near the truth. Driesch and Morgan, 
opponents of Roux’s form of the theory of preformation, found 
in the Ctenophore an organism in which, when one of the two 
blastomeres is isolated, the other develops into a partial larva. 
This indicated a degree of preformation, but not the degree 
held by Roux ; for, first, more than half of the larva was pro- 
duced from the 4 blastomere, and, secondly, when a piece was 
cut out of the fertilized but unsegmented egg, there was still 
a defect in the larva. The conclusion was: There is a rough 
preformation in the cytoplasm, but not, in addition, a qualita- 
tive divison of the nucleus as Roux supposes. On the other 
hand, Zoja found that a whole medusa developed from even & 
rz blastomere. We must recognize, consequently, a series 10 
the capacity of developing a whole from a part, of which the 
medusa occupies one extreme and the ctenophore the other. 
Studies on amphibian eggs were made by Morgan, who foun 
that half or whole embryos may be obtained from the } blas- 
tomere, according as the contents of the egg preserve their nor- 
mal positions or become intermingled by inverting the ¢8& 
and by Herlitzka, who found that the isolated } blastomere of 
Triton develops like the entire egg. All the facts seemed to 
