Dimensions of pneumatophore gases are given in 

 table 2.* After measurement with an ocular micrometer 

 at 27x (maximum reading error = ±0. 03 mm, as determined 

 from replicate measurements on a series of 10 floats), all 

 gases contained in a single float were extruded by pressure 

 into the capillary of a gas analyzer 5 previously calibrated 

 by weighed mercury delivered from a known length of the 

 capillary, and checked for cylindricity. The analyzer was 

 charged with a saturated solution of acidified sodium citrate, 

 a solution having very low gas solubility. The possibility 

 of gas volume change, resulting from a change of surface 

 tension between the gases in contact with the moist walls of 

 the float and the acid citrate, was checked by injecting 

 known volumes of gas, either dry or in contact with seawater, 

 into the analyzer capillary. No measurable volume change 

 was detected. In general, calculation of the volume of the 

 gas phase appears to be in excess of that obtained by direct 

 measurement by a factor of only 0. 2 to 0. 3 mm 3 (table 2, 

 columns 6, 8). 



Temperature differences between the float, when 

 measured beneath the dissecting scope and when placed in 

 the analyzer, were generally within one degree centigrade 

 and never greater than 2„6°C. The maximum volume 

 change that could result from a temperature difference as 

 great as the latter is only 0.8 to 0.9 percent. 



The analyzer capillary can be read with a hand lens 

 to a volume of plus or minus 0. 57 mm 3 . This amounts to an 

 average error slightly less than 7 percent for Group I, table 

 2, and an average of slightly more than 4 percent for Group II. 



The corrected ratio of calculated volume of gas to 

 actual volume measured by extrusion was determined by 

 calculating a pair of ratios, thus: 



calculated volume high high extruded volume range 



, K 



range low low 



to give the maximum range in ratios: 



calc. low calc. high 

 ext. high ext. low 



*See also Appendix B, External Measurements of Nanomia. 



17 



