296 Studies in the Physiology of Fertilization 



in this paper. Thus it is extrcnit'ly probable that tlie results of Exps. 

 XXIII and XXVI arc to be put down to this cause. 



3. The reactions of Ciona and Asterias egg-extracts and of Ciona 

 blood. 



Since spermatozoa show themselves to be so very sensitive to small 

 alterations in the H-ion concentration of the water, it is necessary to 

 test the reactions of the egg-extracts and egg- waters. For if the latter 

 showed a lesser H-ioii concentration than that of normal .sea- water, their 

 stimulating effects on spermatozoa might be due to this cause. 



With a view to settling this, comparative colour tests were carried 

 out with normal sea-water and Ciomi egg-extract, the latter of about 

 the same concentration as that used in the experiments. Three 

 indicators were used\ as is shown in Table XXXVIII. 



TABLE XXXVIII. (2.11.6.) 



Normal water Ciona extract 



a-Naphthol|ibthaleiu, 8 drops in 10 cc. Green Green 



Neutral Red, 2 drops in 5 cc. ... Yellow Yellow 



Phenolphtlmlein, 12 drops in 5 cc. ... Pink V. faint pink 



The first two indicators showed no difference between the reactions 

 of the normal water and of the water containing egg-extract. The 

 phenolphthalein, however, indicated that the extract had a slightly 

 greater concentration of H-ions than the water. If this difference had 

 been in the other direction, it might have explained the effect of the 

 extract on the fertilizing power of sperm. As it is, however, the cause 

 of this must be sought in some other factor, which remains at present 

 undetermined. 



As the extract of the eggs of A.iterius had a reverse effect on sperm- 

 suspensions from the other extracts examined, its reaction was specially 

 investigated with the colour indicators. The results of the tests are 

 given in Table XXXIX. 



TABLE XXXIX. 



' Too much reliance cannot be put on the colour reactions given in this section, since 

 Soreusen, Ergehnisse der Phi/siohgit'. states that the indicators used, namely Neutral 

 Red, a-Naphtholphthaleiu and Phenolphthalein, are not always trustworthy in the 

 presence of proteins. Neutral Red is said to be "kaum brauchbar," and the other two 

 "nur selten." 



