406 E. E. JUST. 



tilize may be due to absence of fertilizin. If normally fertilization 

 occurs during first maturation, the failure of polar bodies to fer- 

 tilize may be due to the fixation of fertilizin ; polar bodies are thus 

 sterile as are all parts of the egg. If it prove that polar bodies 

 lack cortex and are really endoplasmic, this would be suggestive 

 as to the location of fertilizin in such ova, as, for example, As- 

 terias, in which fertilization may take place at various stages of 

 maturation. 



III. 



The experiments above noted show that eggs of Arbacia in- 

 duced through treatment with hypertonic sea-water to initiate 

 mitosis after return to sea-water are capable of giving a response 

 to insemination similar to that in normal fertilization. This gives 

 rise to several considerations. We may discuss these in turn. 



i. In the first place, the stage in mitosis through which an egg 

 is passing at the time of insemination is of no consequence for 

 complete cortical response. Eggs in any stage of mitosis (except 

 the telophase) respond completely to insemination whether or not 

 the spermatozoa entering such eggs take part in the ensuing divi- 

 sions. This would indicate that physical or chemical changes set 

 up in the cytoplasm during mitosis constitute no bar to fertilization. 

 In this respect changes set up by the first cleavage mitosis do not 

 differ from those in the maturation mitoses in those core's that 



o o 



normally take in sperm before complete maturation. Thus 

 changes in permeability, rate of oxidation themselves held as 

 " causes " of fertilization do not interfere with the cortical re- 

 action to sperm. 



If we define fertilization, in terms of this cortical phenomenon, 

 as an instantaneous reaction between some ovogenous substance 

 and the spermatozoon at the time of insemination, the experiments 

 here reported are again suggestive. Of course, the reader may not 

 accept this definition of fertilization ; indeed, it may turn out to be 

 wholly fallacious. Let us, however, for the sake of argument, 

 assume that the definition is correct ; that the primary aim in the 

 fertilization process is the incorporation of the sperm head as part 

 of the zygote nucleus, thus insuring equivalence of maternal and 

 paternal chromatin in heredity ; and that the reaction at the egg 



