STUDIES OF FERTILIZATION. 



235 



and 22 would no doubt disappear. But it is improbable that 

 the general form of the curve would undergo any essential 

 change even with a much more extensive series of determinations. 



3. Curves of Successive Half -dilutions. 



In contrast to these results, and for the purpose of defining 

 the character of the main problem sharply, we may next con- 

 sider the fertilizing power of a series of half dilutions of a I per 

 cent, sperm suspension. The curves from these experiments 

 furnish an almost incredible contrast to the one already given; 

 as an example we may examine the following strikingly regular 

 curve, Fig. 2. The first member of this series was a 1/8 per cent. 



0123456789 10 II 



100 [— ' 1 — \ — I — I I I I t— t—u-I — r-^ ' — r— I — 1 — *■ 



80 

 70 

 60 

 50 

 40 

 30 





Curve 2. 



sperm suspension freshly prepared, thus falling in position 3 on 

 the scale; 8 c.c. of this was taken (No. i); to 4 c.c. of i, 4 c.c. 

 of sea-water was added (No. 2) = 1/16 per cent., (1/2^) ; to 4 c.c. 

 of 2, 4 c.c. of sea-water was added (No. 3) = 1/32 per cent., 

 (1/2^); this was continued eight places to 1/2^°. Four drops 

 of a 10 per cent, egg-suspension was then added to each, and the 

 percentage of segmented eggs was counted three hours later. 

 Plotted they give the above curve. In this case it will be seen 

 that the fertilizing power almost ceases at 1/2^° = 1/1024 per 

 cent, sperm suspension. The eggs and sperm were not at fault 



