2 E. E. JUST. 



August 1914, at the Marine Biological Laboratory, Woods Hole. 

 The majority of the experiments deal with the effect of heat on 

 the Nereis e^g. Under A these experiments are described. 

 Under B are described experiments with KCl. 



A. The Effect of Warming on the Initiation of Develop- 

 ment IN Nereis. 

 Methods. — At first all sea-water used was heated, usually not 

 beyond 75° C, to destroy any spermatozoa possibly present, 

 cooled, and vigorously shaken before the experiment. But this 

 is unnecessary, as my observations showed. I have kept Nereis 

 eggs in sea-water during the cool days of June for thirty-six 

 hours without even jelly secretion. During several seasons I 

 have never found eggs spontaneously developing in sea-water, 

 although eggs occasionally extrude part of their jelly. More- 

 over, in not a single uninseminated control in ordinary sea-water 

 was a developing egg ever found. In many experiments in 

 addition to the uninseminated control a batch of eggs from the 

 same animal as those warmed was inseminated. It was thus 

 clearly proved that the eggs subjected to warming are in no wise 

 abnormal. For fear of contamination, the needless inseminated 

 control was discarded in the later work. 



For a given experiment the following procedure was adopted: 

 A small flask or a large test tube with a measured quantity of 

 sea-water was placed in a large beaker of sea-water. This was 

 warmed over an alcohol flame and the temperature kept constant 

 by the use of thermometers in the flask and in the beaker. The 

 eggs were generally from one female; if from several small ones, 

 they were mixed so that the inseminated or uninseminated con- 

 trols and the warmed eggs were always the same. The eggs in 

 the initial experiments (see below) were either from females cut 

 in the warm sea-water or they were put in the warm sea-water 

 dry; i. e., from a thoroughly dried female which was pricked to 

 cause the escape of eggs. Eggs were also subjected to heat after 

 washing by changing the sea-water several times during various 

 intervals of time. By means of a capillary pipette measured 

 quantities of eggs were transferred after exposure at varying 

 intervals to five or to one hundred c.c. of ordinary sea-water. The 



