STUDIES OF FERTILIZATION. 



237 



diluting the sperm about 1/60. To each of the A series (except 

 i) four drops of the same egg-suspension was then added. The 

 resulting percentages of fertilization are given in Table I. 



If we compare A and B in this table it will be seen that while 

 it is true that B runs out earlier than A , nevertheless the fertiliza- 

 tions in the two series are not proportional to concentrations of 

 sperm; for instance A g at 1/256 per cent, fertilizes 3.5 percent, 

 of the eggs, whereas 5 3 at 1/240 per cent, fertilizes 98 per cent., 

 5 4 at 1/480 per cent, fertilized 60.5 per cent., 5 5 at 1/960 per 

 cent, fertilizes 51 per cent. It is obvious that it is not concentra- 

 tion but condition of the sperm that is significant, which comes 

 out with extreme emphasis in a control of this series. In this 

 control, I drop of ^ (i per cent, sperm) was added to 8 drops of 

 the same egg suspension in 1,000 c.c. of sea-water 2 minutes 

 after the other inseminations, thus making a 1/30,000 per cent, 

 (i X i/iooo X 1/30) sperm suspension; every egg fertilized; the 

 percentage of cleavage was 100 per cent. 



The question then arises, what is this condition of the sperm 

 which causes such loss of fertilizing power? We may note the 

 following points: (i) To bring out the lack of significance of 

 the absolute concentration of the sperm, in several of the experi- 

 ments with successive half dilutions, counts were made of the 

 numbers of spermatozoa seen in the egg- jelly of members of the 

 series with no fertilizations: Thus on July 16 a series of half dilu- 

 tions ran out to o in the seventh crystal (1/128 per cent, sperm) : 

 in ten eggs selected at random from this crystal, an average of 9 

 spermatozoa was counted in the jelly and in contact with the 

 membcane of these eggs; but, as the upper and lower surfaces 



