TX 
THE EFFECT OF ARTIFICIAL MEMBRANE FORMATION 
ON THE EGG 
We shall see later that for the eggs of starfishes and various 
annelids (Polynoe and Thalassema) the induction of artificial 
membrane formation is sufficient to cause some of the unferti- 
lized eggs to develop into larvae. According to the experi- 
ments of Herbst, to which we shall return later, something 
similar appears to be the case exceptionally with the eggs of 
the Neapolitan sea-urchins also. Neither the eggs of the 
Californian sea-urchins, nor those of Arbacia at Woods Hole, do 
as a rule develop into larvae if artificial membrane formation 
alone is produced in them. ‘They do, however, without excep- 
tion exhibit the initial changes of development after such 
treatment. It depends upon the temperature how far they will 
develop. If the temperature is very low (from 2° to 5°) the eggs 
divide very slowly and regularly, and a few may develop into 
swimming larvae,' although they do not survive the blastula 
stage. If the temperature is a little higher, some 6° to 8°, the 
eggs go into the two-, four-, eight-, and even sixteen-cell stage, 
but no farther. At higher temperatures still, say 15° to 18° C., 
a formation of astrospheres and nuclear division takes place; 
but then the development comes to a standstill and the eggs do 
not divide, but slowly disintegrate. 
The fact that the egg can develop at a low temperature to 
the blastula stage, and that nuclear division and cell division 
begin always after the membrane formation, proves that this 
process suffices to set the whole apparatus of development in 
motion. The subsequent treatment with a hypertonic solution 
iLoeb, Untersuchungen weber kiinstliche Parthenogenese, p. 490; Biochem. 
Zeitschr., I, 203, 1906. 
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