CARBON DIOXIDE AS A NARCOTIC AGENT. 



459 



facts is that development is practically suppressed by the higher 

 tensions of CO 2 . The correctness of this view is also indicated 

 by the fact that cleavage was not obtained during prolonged ex- 

 posures to such solutions. 



PER 

 CENT 



lOOh 



75- 



15O 



ISO 



MIN 



FIG. 2. The times required for the appearance of the first cleavage of 

 Arbacla eggs following various lengths of exposure to sea water 80 per 

 cent, saturated with CO.,. Temperature, 2i.2-2i.6. Abscissa time, in 

 minutes, after insemination. Ordinate = percentage of eggs showing the 

 first cleavage. 



Symbol. Length of Exposure. 



9 Dots o minutes 



X Crosses 5 minutes 



O Circles 10 minutes 



Crosses in circles 20 minutes 



A Hollow Triangles 35 (?) minutes 



A Solid Triangles 80 minutes 



For each of the six curves the final value, omitted from lack of space, was 

 100 per cent., except in the case of the twenty minutes exposure, where it 

 was 98 per cent. There have also been omitted the cleavage curves follow- 

 ing exposures of 160, 320, and 640 minutes, which ultimately showed cleav- 

 age in 97 per cent., 99 per cent., and 88 per cent, of the eggs respectively. 

 Table III. gives the delay in 50 per cent, cleavage corresponding to each 

 cleavage curve of the complete series. 



The relation between time of exposure and retardation of de- 

 velopment is shown for a typical experiment in Table III., the 

 values for 50 per cent, cleavage having been taken from the curves 

 in Fig. 2. 



