432 J. GRAY 



This process raises all the physiological activities of the egg to 

 the values reached in a normally active cell, (ii) A develop- 

 mental phase, whereby the necessary machinery for development 

 is introduced into the egg in the form of an artificially produced 

 aster. 



It has been stated, however, that the theory of fertilization 

 advanced by F. R. Lillie is based on a very different series of 

 facts to that of Loeb. Lillie's theory is based on the behaviour 

 of the normal gametes. It is necessary for any alternative 

 theory to cover the whole of the facts. 



Lillie has shown that sea-water which has been in contact 

 with the unfertilized eggs of the same species has a remarkable 

 effect on the spermatozoa. Such sea-water contains a substance 

 which (i) usually causes a marked increase in the activity of the 

 spermatozoa, (ii) causes them to form macroscopic clusters — 

 usually rounded in shape — of intensely active sperm, (iii) in 

 some cases causes the spermatozoa to adhere to one another 

 for a considerable time, in large immobile clumps. The essence 

 of Lillie's theory is that fertilization is effected by the union 

 of the egg and the sperm by this intermediate and specific 

 substance (given out by the unfertilized egg) which Lillie calls 

 ' fertilizin '. The sperm contains a substance which is agglu- 

 tinated by fertilizin, and so the sperm becomes attached to the 

 egg. Immediately fertilization has been effected the produc- 

 tion of fertilizin ceases, and so no more spermatozoa can adhere 

 to the egg. 



I think it is a just comment to say that the above theory 

 (with its marked analogy to the side-chain theory of Erhlich) 

 does not purport to indicate the nature of the forces, physical 

 or chemical, which underlie the various processes of normal 

 fertilization. It does, however, stress the necessity of the 

 existence of specific substances, ' fertilizin, &c.\ without which 

 union between egg and sperm is impossible ; further, Lillie 

 makes no attempt to extend his theory to the process of 

 artificial parthenogenesis. Let us attempt to examine the 

 properties of ' fertilizin " from a physico-chemical point of view. 



The presence of fertilizin usually stimulates normal sperma- 



1 



