134 PROCEEDINGS OF THE AMERICAN ACADEMY. 



perimerits were all made on eggs of Toxopneustes variegatus. 2 Obvi- 

 ously the first point to be determined was the size relations of the 

 larvae developing in various alkaloid solutions. As the outcome has 

 shown no marked influence in the direction of either an increase or a 

 decrease in size, it is clear that no basis for a cytological study pre- 

 sented itself. 



This work was done at the Bermuda Biological Station during the 

 past summer, and it gives me pleasure to express my thankfulness to 

 Dr. E. L. Mark, the Director of the Station, for the many courtesies 

 extended me while there. 



Experiments with Atropine Sulphate and Pilocarpine 



Hydrochloride. 



Bearing in mind the fact that the developing echinoderm eggs are 

 very sensitive to changes in their environment, and are more or less 

 easily affected by external conditions, a few special precautions were 

 taken in carrying out the experiments. The eggs to be fertilized were 

 kept in finger bowls containing sea-water about an inch deep, and 

 were mixed with very small quantities of the spermatic fluid. In this 

 way there was eliminated a possible disturbing factor due to the dis- 

 integration of superfluous sperms. The eggs were allowed to settle 

 to the bottom of the dish and then transferred to finger bowls each 

 containing 300 c.c. of the solution to be tried. To insure also an 

 equal distribution of eggs among the several dishes, thus avoiding 

 another possible source of error, the same number of drops of fluid 

 containing the fertilized eggs was added, by means of a pipette, to each 

 dish. It goes without saying that each experiment had its own 

 control, and that the eggs of the same individual were used in both 

 experiment and control. 



The eggs were examined at intervals, and outline camera drawings 

 were made of the developing larvae. If any differences in the larvae 

 of a set were observed, drawings were prepared of each type sepa- 

 rately. Besides, the drawing of each larva was compared with a few 

 other larvae, so that every drawing was representative of a number 

 of larvae. These drawings served later for reference, and also for 

 a comparison of the sizes attained by embryos in different solutions. 



Measurements, wherever such are given, were made on the draw- 



2 Toxopneustes variegatus is found in great abundance in Bermuda, and its 

 eggs may be easily obtained, according to the writer's observation, from about 

 the middle of May till the middle of August, June and July being the most 

 favorable period. 



