114 H> Hl NEWMAN. 



sterilizing the sea water in order to avoid normal fertilization. 

 Although he does not mention the fact in these particular experi- 

 ments, his practice was to use boiled or highly heated sea water ; 

 while I used sea water that had been kept in a demijohn for at 

 least four days. It seems barely possible that heating of the 

 water prevents spontaneous membrane formation. I would, of 

 course, have tried this experiment, had I known of Loeb's detailed 

 paper at the time of my experiments, but I had with me only his 

 book on " Artificial Parthenogenesis and Fertilization " and in 

 that book he fails to mention the occurrence of spontaneous 

 parthenogenesis in Asterina. Heated sea water would doubtless 

 be relatively poor in oxygen and this might be responsible for his 

 failure to find spontaneous membrane formation. It is possible 

 also that this process (membrane formation) was so belated in 

 its appearance that it occurred after Loeb had ceased to look for 

 it in his cultures. Unless one gets a very early start in experi- 

 ments with this material the working day is likely to be over 

 before any signs of membrane formation appear, and the next 

 morning these eggs will have undergone cytolysis and their mem- 

 branes will have disappeared. My plan was to make a before- 

 breakfast expedition to the collecting grounds, get the material 

 ready for work, breakfast, and be ready for experimentation by 

 8:00 A.M. If one begins to collect after breakfast it is likely to 

 be nearly 11:00 A.M. before experiments with Asterina eggs 

 could be commenced. If such were the case it would be 6:00 

 P.M. before distinct membranes would be visible, later than the 

 time when the investigator habitually " knocks off for the day." 

 It is barely possible then that Loeb may have missed spontaneous 

 membrane formation in some such way as this. 



Of the validity of my obervations there seems to be no doubt. 

 In answer to the criticism that failure to heat the sea-water 

 vitiates the observations, it may be said that if these eggs with 

 membranes are fertilized, they should segment ; but they never do. 

 We seem to be forced to the conclusion, therefore, that membrane 

 formation in Asterina, which Loeb has been at such pains to bring 

 about by chemical means, occurs spontaneously in a considerable 

 percentage of cases. This being true, the various manipulations 



