282 HELEN DEAN KING. 



B. EXPERIMENTS WITH THE EGGS OF Chatoptems pergamentaceus. 

 ' As the eggs of Chcctopterus could be obtained in considerable 

 numbers at Woods Hole in the summer of 1909, experiments wrre 

 made to study the influence of amido-acids on the early develop- 

 ment of this annelid, in the hope that some definite alterations 

 in development might be produced comparable to those obtained 

 by Loeb ('oi) and by Lillie ('02) when eggs of Chcetoptenis were 

 treated with potassium salts. Material intended for micro- 

 scopic study was preserved in Boveri's picric-acetic solution 

 and stained with luematoxylin. 



Cyst in. On the morning of August 6, 1909, a lot of Chcetopterus 

 eggs was placed in 100 c.c. of a saturated solution of cystin as 

 soon as the polar bodies had been extruded. The early develop- 

 ment of these eggs was slightly accelerated, and swimming 

 larvae were found in this culture nearly one half hour before any 

 movement could be detected in the control larva?. The next day 

 the cystin solution was swarming with well-developed trocho- 

 phores, but they all died about fifty hours after the experiment 

 began. No abnormal embryos were noted at any stages of 

 development and none were found in preserved material. 



The experiment was repeated several days later with eggs from 

 another female. The results obtained were practically the same 

 as in the first experiment, since there was more rapid develop- 

 ment during the segmentation period. The solution proved to 

 be toxic after thirty hours, however, killing the embryos without 

 producing any alterations in structure. 



Leiicin. In one series of experiments this substance was used 

 on the eggs of Ch&topterus in solutions of the following strengths: 

 2 , YJ- and TjJ-g- per cciu . None of these solutions had any marked 

 effects on the early segmentation of the eggs, but they evidently 

 caused a slight acceleration in development during a later period 

 as the larva' in all of the solutions began moving some thirty 

 minutes before there was any movement of the control larvae. 

 Twenty hours after the experiments were started all of the cul- 

 tures were carefully examined. The majority of the eggs that 

 had been treated with the }/ per cent, solution had stopped their 

 development in the blastula stage, and were lying at tin- bottom 

 of the dish apparently dead; a very few larva? were swimming 



