262 CARL R. MOORE. 



atory live-car and was kept in running sea-water in the laboratory 

 until used. Eggs and sperm were secured in the usual way 

 by cutting away the leathery oral disk and collecting the eggs 

 and sperm in separate Syracuse dishes as it is shed by the animal. 

 Eggs were always washed in sea-water from two to four times 

 before being used in an experiment, as this insures a more con- 

 sistent lot of fertilizations than with unwashed eggs. 



The method for testing the capacity for fertilization of eggs 

 that have been activated by a hypertonic solution is the same 

 as that employed by Loeb 1 in his studies of this nature. Eggs 

 after washing were transferred to the hypertonic sea-water and 

 allowed to remain for definite periods of time: at the termination 

 of the exposure they were removed with a pipette to two separate 

 dishes of sea-water (150 c.c.-2OO c.c.) A and B. Lot A was 

 allowed to stand at room temperature without further treatment, 

 while to lot B was added a quantity of a fresh sperm suspension. 

 For each experiment both a fertilized and an unfertilized lot 

 were set aside as controls. 



III. OBSERVATIONS OF LIVING MATERIAL. 



Since there is a great difference in the effects of different 

 concentrations of, and variable time exposures to, hypertonic 

 sea-water the experiments with the sea-urchin egg have included 

 quite a range of concentrations and periods of exposure, but to 

 simplify the data, only results from two concentrations of the 

 hypertonic solution will be reported at this time. The two 

 concentrations may then be known as the weaker solution (50 

 c.c. sea-water + 8 c.c. 2.\ m. NaCl) and the stronger solution 

 (50 c.c. sea-water + 16 c.c. 2\ m. NaCl). 



These two concentrations of hypertonic sea-water were em- 

 ployed because of the very different results obtained with them. 

 An exposure to the weaker solution results in the segmentation 

 of a relatively few eggs (see Table I. and Fig. i, a) but usually a 

 very small percentage of the eggs will segment once or twice 

 and cease their development, while a similar exposure to the 

 stronger solution gives a much higher percentage of cleavages 

 and a much greater number of swimming larvae. An exposure 



1 " Art. Par. and Pert.," pp. 235-236. 



