H. M. FucHS 295 



One further experiment was carried out, in which a comparison was 

 made between the effects of normal water and t)f three increasing con- 

 centrations of acid water on the fertilizing power of a sperm-suspension 

 of Giotm., used to effect a particular cross. 1 cc. of sperm-suspension h 

 was pipetted into each of four dishes containing (1) 100 cc. normal sea- 

 water, (2) 100 cc. acid water A, (3) 100 cc. acid water B, (4) 100 cc. acid 

 water C. 10 cc. of each was then poui'ed on to separate approximately 

 equal quantities of Ciona eggs G. 



The acid waters were made up as follows : 



A. -2 cc. N/10 HCl in 100 cc. sea-water (V. light green 



with ct-Naphtholphthalein). 



B. •4cc. N/10 HCl in 100 cc. sea-water (Light brown 



with a-Naphtholphthalein). 



C. -6 cc. N/10 HCl in 100 cc. sea-water (Light pinkish 



brown with «-Naphtholphthalein). 



The result of the experiment is given in Table XXXVII, which 

 shows that in this case even the least increase in the H-ion concen- 

 tration of the water completely inhibited the fertilizing power of the 

 sperm-suspension. 



TABLE XXXVIL (31.1.5.3.) 



Normal water Acid water A Acid water B Acid water C 

 Cross : Glh 89 



The first experiment on the effect of Arhiicia egg- water on Giona 

 sperm (Table XXIII) showed inhibition of the fertilizing power of the 

 latter, and the first experiment on the influence of Strongylocentrotus 

 egg- water on Ciona sperm (Table XXVI) showed no change in the fer- 

 tilizing power. It was seen that on the repetition of these experiments 

 with egg-waters whicli had stood for a shorter time with a relatively 

 smaller quantity of eggs, the fertilizing power of the sperm was 

 increased in the same way as it was by treatment with the egg-extracts. 

 It was suggested that the results obtained in the experiments' of Tables 

 XXIII and XXVI were due to the presence of acid in the egg- waters. 

 The egg-water used in Table XXVI gave, at the time fertilization was 

 made, a pink colour with a-Naphtholphthalein (p. 2S5), whereas the 

 normal sea-water gave green. Tables XXXVI and XXXVII show that 

 a lesser increase in the concentrations of H-ions in the water than is 

 enough to give a pink colour with the indicator will quite inhibit the 

 fertilizing power of sperm-suspension of Ciona, — at any rate of suspen- 

 sions of about the strength of those used in the experiments described 



