AUTO-PARTHENOGENESIS IN ARBACIA AND ASTERIAS. 4OI 







less than is required to prevent fertilization is perfectly intelligible 

 on Lillie's assumption that sperm-bound fertilizin is activated 

 and has a greater affinity for the egg-receptors than free fertilizin. 1 



AN ATTEMPT TO CONSTRUCT A PROVISIONAL WORKING 



HYPOTHESIS. 



Although no final interpretation of the phenomena of fertiliza- 

 tion is possible at the present time, an attempt to formulate 

 some viewpoint which does no violence to our knowledge, and 

 which at the same time may serve as a working hypothesis, 

 must be made for further guidance. 



If we accept the evidence of F. R. Lillie, together with my 

 verifications and additions to it, and remember that many of 

 the facts discovered by Lillie, as well as some found by myself, 

 are the direct products of the fertilizin theory considered as a 

 tool, I think we may even now admit that it is a useful working 

 hypothesis. Lillie ('13) himself has emphasized this point, and 

 moreover has listed among the other advantages of his theory, 

 that it gives us an explanation of the specificities of fertilization; 

 may furnish the foundations for the chemical conceptions needed 

 by any theory of fertilization, and above all, that it offers one 

 explanation for the initiation of development, whether by fer- 

 tilization or parthenogenesis. 



To what extent these claims are justified, and to what extent 

 the theory will undergo modification, it would be unprofitable 

 to discuss at present. One claim and its consequences however 

 does invite discussion at the present time, and in this connection, 

 for if the fertilizin theory is really capable of unifying the various 

 methods of inducing parthenogenesis, its relations to another view, 

 which apparently does the same thing must be analyzed, and 

 furthermore we must answer the question whether all cases of 

 parthenogenesis are really instances of auto-parthenogenesis. 



1 Since Purple X also appears when spermatozoa come into contact with the 

 secretion, it is possible that its appearance plays a role in the prevention of poly- 

 spermy. This would not prevent a similar effect on the part of the anti-fertilizin, 

 as suggested by F. R. Lillie. Indeed the chances that any particular sperm will 

 complete the reactions postulated by the theory, must be exceedingly small when 

 we reflect on the immense numbers which collect about each egg. Such collections 

 become more intelligible when we recall that whereas the biparental effect can be 

 carried out by a single sperm, the initiatory effect, at least in Arbacia ('is 1 ) requires 

 more than five. 



