4S ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
it, even after the work of Herold and von Siebold.” In order 
to increase the number of Bombyx eggs that develop without 
fertilization, Tichomiroff used a method of which the breeders 
avail themselves in order to accelerate the development of 
fertilized eggs. Certain kinds of silkworms lay their eggs in 
the summer and these eggs begin to develop at once; but 
during the winter the development ceases, and the caterpillars 
do not hatch till the spring. Now it appears that it is cus- 
tomary among the breeders to hasten the development of the 
fertilized eggs by special “stimuli,” so that the caterpillars 
hatch out in the same summer in which the eggs are laid. 
Tichomiroff applied the same methods to unfertilized eggs. 
The experiments consisted in stimulating eggs mechanically and 
chemically in the same way as is done in order to obtain caterpillars 
in the same summer from fertilized eggs which normally only develop 
to a certain stage in summer. I plunged thirty-six unfertilized eggs 
into concentrated sulphuric acid and left them there two minutes 
(afterward the eggs were scrupulously washed). Thirteen of these 
eggs began to change color on the fourteenth day. On the sixteenth 
day an embryo could be perceived in these eggs. Both the embryo and 
the serous envelope consisting of magnificent pigment cells appeared 
quite normal. 
Sixteen other eggs were rubbed quite lightly with a brush. Up till 
now (after one week [?]) the result has remained negative: not a 
single egg has developed. A third batch of ninety-nine eggs were 
brushed hard. On the fourth day the color change characteristic 
of developing eggs was observed in six of these eggs. Not a single 
parthenogenetically developing egg was observed among all the 
unfertilized eggs which remained unstimulated. 
The breeders’ experience that the immersion of eggs in 
concentrated sulphuric acid, or brushing them, accelerates 
development, is hard to explain. Both rubbing the eggs with 
a brush and plunging them into sulphuric acid may serve, 
perhaps, to injure or alter the skin of the egg, whereby it 
becomes more permeable to oxygen. We shall see later that 
