52 



SCIENCE 



[N. S. Vol. XLIII. No. 1098 



If this substance be present in the egg in 

 adequate amount, the egg can be fertilized, 

 otherwise not. It may be obtained in solu- 

 tion in the sea-water and recognized by its 

 capacity for agglutinating sperm suspen- 

 sions of the same species, in some cases at 

 least. If it is thus possible to associate the 

 fertilizable condition of the ovum with a 

 definite substance, we have a base from 

 which an analysis of fertilization can be 

 made. 



If the existence of such a substance be 

 admitted, it must operate either by activa- 

 ting some substance in the spermatozoon, 

 which is to be regarded as the effective 

 agent in subsequent changes, or we must 

 regard it as the effective agent which is 

 transformed from an inactive to an active 

 state by some substance in the spermato- 

 zoon. If we take the first alternative, we 

 have no explanation of parthenogenesis, 

 whereas if we regard the egg substance as 

 the active agent, the explanation of parthen- 

 ogenesis proceeds along the same lines as 

 that of fertilization. Moreover, I have been 

 able to show by an analysis of the phenom- 

 enon of blood inhibition of fertilization, 

 that the first point of view is untenable. 



This substance may therefore be called 

 the fertilizing substance, or fertilizin. By 

 its reaction it is shown to be a colloidal sub- 

 stance, not giving the iisual protein tests, 

 and exhibiting some of the properties of a 

 ferment as shown by Richards and Wood- 

 ward. Fertilization would thus be a three- 

 body reaction between the sperm-receptors, 

 fertilizin and egg-receptors linked in line; 

 and it is possible to show that inhibiting 

 agencies may operate at the various link- 

 ages of such a reaction. In its reaction 

 with the sperm the fertilizin of different 

 species exhibits a certain degree of speci- 

 ficity, which should be more fully studied, 

 but which has been partly explored by 

 Jacques Loeb and myself. 



This form of hypothesis takes into ac- 

 count the internal factors both of maturity 

 of the germ-ceUs and their specificity; it 

 is also adapted to explain the environmen- 

 tal conditions of fertilization extremely 

 well; and it is consistent with the results 

 of parthenogenesis, and the kno\\Ti relations 

 of parthenogenesis and fertilization to the 

 permeable or impermeable conditions of the 

 egg-membrane. 



I believe that I speak for all naturalists 

 when I express my admiration for the ad- 

 vances in the conception of the cell due to 

 the labors of many physiologists. But those 

 of us who deal with the more complex 

 phenomena of cell-life as shown in fertiliza- 

 tion, in the behavior of chromosomes, and 

 in the phenomena of heredity, feel that no 

 advance in our comprehension of the cell- 

 membrane, of the relation of cell-activity to 

 electrolytes, nor of the chemical analysis 

 of triturated cells, will lead to a fundamen- 

 tal comprehension of these phenomena. 

 There is a great gap in our knowledge of 

 cellular physiology, the significance of 

 which is not generally appreciated. "We 

 know nothing except what our microscopes 

 show us, of the reactions of the colloidal 

 substances of the living cells; and all hope 

 of a physico-chemical analysis of cell ac- 

 tivities is premature until the gap is filled 

 in. 



The main physiological problems of fer- 

 tilization are still before us; all the work 

 up to the present has merely prepared the 

 way for their solution. Fertilization is the 

 knot in the webs of successive generations 

 which must be untied before we can trace 

 the strands from generation to generation. 

 The task bespeaks all that we know, or may 

 hope to know, of cellular physiology. As 

 in all times of the history of the subject 

 our vision is limited by our general biolo- 

 gical conceptions, and the problem will 

 move forward as our general knowledge of 



