H. M. FucHS 283 



Given aniaunts of Ciona sperm-suspension (set' Table XXII) were added 

 to (1) 3 cc. plain sea-water, and (2) 3 cc. Arbacia egg-extract. 10 cc. 

 water was then added to each, and they were poured on to approximately 

 equal amounts of Ciona eggs. Each experiment was double, two 

 different quantities of sperm being used. 



From Tables XXI and XXII it is seen that percentages of eggs 

 fertilized in Ciona by a certain concentration of sperm is raised by 

 treatment of the sperm with Phallusia or Arbacia extract, in the same 

 way as it was by treatment with extract of the eggs of the same species. 



TABLE XXII. (38.6..5.) 

 ( 3 drops sperm 



Exp. 1. Ajh ^ ^2 



Exp. -1. C/d j.^ 



3 drops sperm 

 2 



( 3 drops sperm 



Exp. 3. t'A -^ ^^ 



3. Arbacia e(/g-water. 



To obtain the egg-water, the eggs (jf Arbacia were allowed to stand 

 in little more than their own volume of water for 4£ hours. Given 

 amounts of Ciona sperm-suspension (see Table XXIII) were added to 

 (1) 1 cc. plain sea-water, and (2) 1 cc. Arbacia egg-water. The latter 

 contained the Arbacia eggs, and was not drawn off free of them, as in 

 previous egg-water experiments. To each of the dishes was then added 

 10 cc. water, and they were poured on to equal amounts of Ciona eggs. 

 The experiment was double, being made for two different concentrations 

 of sperm. 



TABLE XXIII. (35.25.4.) 



Egg-water 



contaiuing 



Water Arbacia eggs 



_ , ,, \ 3 drops sperm ... 67 



Oross, A/lj ^ ^Q ^^^p^ ^p^^,^ ^^ ^^^ ^ 



The complete inhibition of cross-fertilization of Ciona by sperm 

 treated with Arbacia egg-water, as seen in Table XXIII, was unex- 

 pected, more especially as A rbacia egg-extract had had the opposite effect. 

 It was thought that the result might be due to the presence of 

 numerous Arbacia eggs in the sperm-suspension which was used to 

 effect the fertilization. The Ciona spermatozoa might conceivably 

 have become entangled in the jelly surrounding these eggs. A second 



