EFFECTS OF HEAT ON TOAD S EGG. 



229 



TABLE I. 



stops their development before gastrulation begins, sections of 

 the eggs show, in many cases, that the greatest injury has been 

 produced in the yolk portion of the egg which is frequently 

 vacuolated and not segmented although the upper part of the 

 egg has divided into a large number of small cells. Hertwig 

 has noticed the same phenomenon in some of his experiments, 

 and in explanation he states as follows : " Dass Froscheier bei 

 erhohter Temperatur zunachst partiell geschadigt werden und 

 eventuell absterben, ist offenbar auf die verschiedene Organisa- 

 tion der animalen und vegetativen Halfte der Dotterkugel zuriick- 



