H. M. FucHS 297 



Both indicators show that the water containing the Asterias extract 

 has a considerably greater concentration of H-ions than normal sea- 

 water. The colour given by the Asterias extract with a-Naphthol- 

 phthalein approximates to that given by the "acid water" of Exp. 1, 

 Table XXXVI, and by "acid water A" of Table XXXVII, both of 

 which inhibited the fertilizing power of Giona sperm-suspensions. If 

 one assumes a like action on Strung tjlocentrotus sperm, the " poison " for 

 the latter which is contained in A sterias eggs may be the presence of 

 an acid. This is, however, only a suggestion which remains quit(> 

 unproved. 



Finally, colour tests were made with the blood of Ciona to see 

 whether the change in its effect on the fertilizing power of Ciona sperm, 

 according to the time the animals from which it is taken have been in 

 the Aquarium, is correlated with any change of reaction. It will be 

 remembered (see p. 281 seq.) that the blood of animals taken fresh 

 from the sea increased the fertilizing power of sperm-suspensions, while 

 a sojourn of the animals for even one night in the Aquarium water 

 reversed the etfect of the blood on the sj^erm. 



For the colour tests the blood was first centrifuged in order to obtain 

 the liquid fairly clear and colourless. The plasma showed a red colour 

 with Neutral Red, yellow with Methyl Orange and pink with a-Naph- 

 tholphthalein. There was no alteration in the reaction when the 

 animals had been kept in the Aquarium, the latter experiments being 

 made with animals from the lot used in Series D and E, Table XIX. 



The fact that the blood gave a pink colour with a-Naphtholphthalein 

 shows that it has a concentration of H-ions considerably greater than 

 that of normal sea-water. Tables XXXVI and XXXVII showed that if 

 acid is added to the latter until it gives a pink with this indicator, the 

 fertilizing power of sperm-suspensions made up in it is completely 

 inhibited. From this it follows that there must be something in the 

 blood of fresh Ciona which ct)unteracts the effect of this acidity as well 

 as stimulates the spermatozoa. It might be added as a suggestion that 

 if this stimulating substance disappeared from the blood after the 

 animal had been kept in the Aquarium water, the acidity of the blood 

 would have the effect of paralyzing the spermatozoa, which would be a 

 possible explanation of the observed phenomena. 



