SPONTANEOUS MOVEMENTS IN LARV.-K. 415 



average of 3 observations for each minute), and the average of 

 all the individuals for each concentration of CO 2 was indicated 

 on the charts for each two minutes by the number of spaces 

 above the base line. 



RESULTS. 



In the lir-i -tage 3 or 4 specimens can be studied at the same 



time in 01 < riment; but in the free swimming stage only 



one -penmen r.m be recorded at a time. The breeding period 



of thi> spe< ies i- brief, hence, the number of individual record- 



obtainable i- not as large as is desirable, but when the averages 



brought i..-i-ther the conclusions stated below seem justified. 



I'.ut tin number is insufficient to give a smooth contour to a 



rur\e indicating the effect of any given concentration \\itli 



the time of exposure or to state in an exact manner 



tin rt: different concentrations. 



Tl rt records indicate the following relation between 



change- iii the partial pressure of CO 2 and the body movements 

 and respiratory rate. 

 .1. Body movements. 



I. Tlu- movements in each group show an increase 

 during the first few minutes following an increase 

 in the concentration of CO 2 . 



j. \Vlim the specimens in the water containing the 

 higher concentration of COj are returned to norm.il 

 sea water, the movements in each group are de- 

 pressed considerably below the normal. Thi> 

 depression is very pronounced during the first 10 

 minutes and gradually approaches the normal 

 during tin- ,v minute period. 



3. Thr intensity of the reaction varies with the increase 



in ('(^2, up to the middle range of concentration; 

 above this the intensity of stimulation decreases 

 with the increase of CO 2 concentration. 



4. The reaction to increased CO 2 is less intense but of 



< ater duration in the earlier than in the later 



stage. On returning to normal sea \\ater the 



depression of movement is less in the earlier than 



in the later stage and recovery is slower. 



The different effects in the two stages are not easy to explain. 



