8 E. E. JUST. 



With dry eggs one may obtain lOO per cent, cleavage; with the 

 eggs cut from worms in warm water one never gets more than 8 1 

 per cent, the average being very much lower as the figures given 

 above show. With both kinds of eggs 20 per cent, swimming 

 forms is the maximum, the optimum exposure for the various 

 temperatures used being the same. 



Experiments show that the use of warm "egg- water" does not 

 improve the results. 



3. The Experiments with Serum Eggs. 



The effect of warming Nereis eggs in the body fluids was studied 

 with difficulty mainly because of the scarcity of body fluid in 

 Nereis. As Lillie has pointed out this worm is little more than a 

 bag of eggs. The amount of blood present is negligible and 

 unavailable for. warming experiments. I therefore adopted the 

 method used by Lillie — that of cutting up spent females. In his 

 study this juice gave results comparable to the perivisceral fluids 

 in Arbacia. For an experiment I minced as many spent females 

 as I could get, using a small quantity of sea-water; the juice thus 

 obtained is designated as "serum." While I think that my 

 experiments with this serum are conclusive I wish to point out 

 that Nereis is not the most favorable form with which to establish 

 the fact of serum inhibition — certainly this is true for the method 

 I used. It may be stated at the outset that as Lillie found for 

 both Nereis and Arbacia I have found repeatedly that the 

 ' ' serum ' ' of Nereis quite definitely inhibits fertilization. Further- 

 more, just as definitely does the serum inhibit initiation of de- 

 velopment with warming. I cite experiments to give the details : 



(a) July 15, 10:55. Eggs from one fine large female previously 

 dried are divided into four lots. Eleven spent females are finely 

 minced to procure twenty drops of "serum." Ten drops of the 

 "serum" is added to each of two dishes containing 3 c.c. of sea- 

 water; eggs added to both. One lot is warmed at 34.5° C. — 

 Lot A ; Lot B inseminated. Samples of A are taken at five-minute 

 intervals up to 11:35. 2:00 P.M., i per cent, of cleavage in 

 both lots. Next day no swimming forms in either. Eggs from 

 the same female, Lot C, warmed in sea-water and Lot D, in- 

 seminated, develop. 



