242 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
and fertilization with sperm curtails the life of the larvae, and 
prevents them from reaching the pluteus stage. For if we start 
the eggs developing by the old osmotic method, 1.e., with 
gelatinous membrane formation, and then fertilize a cell of 
the two- or four-cell stage with sperm while they are still ready 
to segment, the next division of each of these blastomeres will 
lead to the formation not of two cells, but of three or four. 
To the astrospheres which are already formed in the cell by 
the onset of parthenogenetic development, there are added 
also the astrospheres formed through the influence of the 
spermatozoon; thus the next division of the nucleus of such a 
cell leads to the formation of more than two daughter nuclei, 
which are also usually qualitatively unlike. They are there- 
fore in the position of an egg fertilized by two spermatozoa, 
and so have the same restricted vitality as is possessed by such 
eggs. It is possible, however, that fragments which are ferti- 
lized by sperm while they are in the process of partheno- 
genetic cell division suffer more than normal eggs fertilized by 
two spermatozoa. 
