268 Studies in the Phijsiology of Fertilization 



5. Gomparison of the effects of egg- and ovary-extracts on the 

 fertilization in Ciona. 



The increase in the number of eggs fertilized in the presence of the 

 extracts might be due to some substance contained in ripe eggs alone. 

 In the case of the ovary-extract, it would then be derived from ripe 

 eggs present in the lumen of the ovar}'. Whether this is so, or whether 

 the substance is contained in the ovarian tissue itself can be determined 

 by making a comparison of the effects of equal concentrations of egg- 

 and ovary-extracts on the fertilization. The following experiment was 

 made to determine this point. 



Approximately equal numbers of B eggs were placed in 16 cc. of 

 (1) water, (2) A egg-extract in three concentrations, (3) A ovary-extract 

 in three corresponding concentrations. The strongest egg- and ovary- 

 extracts were made up in approximately equal conceritrations by taking 

 as nearly as possible equal volumes of eggs and ovary, and washing the 

 juices into equal quantities of water. Fertilization was effected by 

 the addition of one drop of c sperm-suspension to each of the dishes. 



TABLE VII. (20.4.2.) 



16 cc. water IS ec. water 8 cc, water cc. water 



cc. extract 1 cc. extract 8 cc. extract 16 cc. extract 

 Cross : ll/c, A extract 



Egg-extract...) ^ (2 13 33 



Ovary-extract ( (3 21 36 



The Table shows that an increasing number of eggs were fertilized 

 in increasing concentrations of both egg- and ovary- extracts. The 

 numbers were, however, not identical in corresponding concentrations 

 of the two extracts, so that the presence of the substance which aids 

 fertilization in equal amounts in both ripe eggs and ovary is not proved. 

 Indeed the ovarian extract had a greater effect than that derived from 

 the eggs. It must be remembered, however, that it is exceedingly 

 difficult to obtain egg- and ovary-extracts in exactly equal concentra- 

 tions, and to such a difference in concentration the differences in effect 

 shown in the Table might easily be due. 



6. Cumparison of the effects of "foreign" and "own" egg-extracts 

 on the cross-fertilization percentages in Giona^. 



The experiments with egg-extracts were originally made to test 

 whether there is some substance in the eggs of Giona which hinders 



' "Foreign" means from another, and "own " from the same individual. 



