1 86 ANIMAL AGGREGATIONS 



isolated for about i hour is at the rate of 219.6 cc. per hour and kilo- 

 gram; for those isolated for about 24 hours it is 77 cc. per hour and 

 kilogram; for those bunched approximately an hour, 160.5 ^^d for 

 those bunched for about 24 hours, 130.2 cc. per hour and kilogram. 

 Similar calculations for the Tracliconiscus show a mean oxygen con- 

 sumption of 263.5 cc. per hour and kilogram when isolated less than 2 

 hours, and of 196.7 cc. when bunched about the same time.^ 



STARFISH RESPIRATION 



The marine ophiurid starfish, phylum Echinoderma, stands well 

 removed from the land isopod, phylum Arthropoda, in the evolution- 

 ary scale and in habitat. The oxygen consumption of isolated and of 

 bunched Ophioderma was tested by Winkler's method. 



A typical experiment was made on three groups of 8 animals each, 

 selected so that there would be the same size relations in each group. 

 The members of each lot were momentarily dried on filter paper and 

 weighed in a known amount of sea-water. The lot weighing most 

 was placed together in a bottle holding approximately 8 liters (ac- 

 tually 8,500 cc); the lot weighing next most was separated, and 

 each individual was placed in an Erlenmeyer flask of about i liter 

 capacity (actual average 1,143 cc). The third and lightest group of 

 8 animals were placed together in a second bottle like the first. Ap- 

 propriate blanks were run on both sizes. All bottles and flasks were 

 fitted with rubber stoppers, which carried tubes for drawing titra- 

 tion samples without contact with air and with a minimum disturb- 

 ance. The containers were gently reversed twice just before sam- 

 pling to insure an even mixing of the sample, and other due experi- 

 mental precautions were taken. Determinations were made 4 hours 

 after the start of the experiment to determine initial relations. Later, 

 tests were made at 24-hour intervals, except that during the middle 

 course of some experiments they were made at 48-hour intervals. 



' Hyman (1923) found the oxygen consumption of the anterior pieces of Planaria 

 dorotocephala to be at the rate of 260 cc. per hour and kilogram. Krogh (1916) lists a 

 rate in calories equivalent to 393.6 cc. per hour and kilogram for Apis meUifica, and 

 of 72 and again of 11 5.2 for Musca. The highest rate listed in Krogh's tables for 

 crustaceans, all gillbreathing, is of 6.528 cc. per hour and kilogram. The values given 

 above for land isopods are subject to a calibration error of about 5 per cent. 



