182 



ON THE RESPIRATOKT ACTION OP WATER-BEETLTIS. 



Eose at 3.53 for 35 sees. 



Eose at 4.27 for 30 sees. 



Observation ceased at 4.43 p.m. 

 No, 3. Aug. ?, 1874. — Observation commenced at 2.31 p.m. 

 on one c? -D- marginalis. 



Eose at 2.50 for 2 sees. Eose at 3.26 for 5 sees. 



» 2.56 „ 35 „ „ 3.38 „ 97 „ 



„ 3. 9 „ 60 „ „ 3.57 „ 97 „ 



Observation ceased at 4.11 p.m. 



Totals 



309 



37 



1993 



Summary. — The male of D. marginalis rose, on an average, 

 once in about 85 minutes for breathing ; and remained, on an 

 average, about 54 seconds at surface for each respiration. The 

 longest interval it was observed to pass without breathing was 19 

 minutes. The duration of a respiration varied from 5 seconds to 

 300 seconds ; and the time it was exposed bore to the time it was 

 quiescent a ratio of 1 : 95. 



XVII. Dttiscus marginalis, 2 . 



No. 1. Aug. 2nd, 1874. — Observation commenced at 7 p.m. on 

 one female. 



Eose at 7. 8 for 20 sees. 

 7.22 „ 80 „ 

 7.38 „ 100 „ 



Eose at 7.50 for an instant. 

 7.54 „ 80 sees. : 

 8.15 „ 280 „ 



Observation ceased at 8.23 p.m. 



No. 2. Aug. 9th, 1874. — Observation commenced at 3.40 p.m. 

 on two females of D. marginalis :— 



