662 THE RESPIRATION AND [pt. m 



short time. Lite & Whitney found that by vigorously aerating the 

 water in which the eggs of Brachionus and Asplanchna were lying, they 

 could make the thick-shelled ones develop as fast as the thin-shelled 

 ones, and hatch as soon. They concluded, therefore, that the re- 

 spiratory rate is much influenced by the amount of air available 

 and that the developmental rate follows it. 



Quantitative experiments were made by Buglia on the eggs oiAplysia 

 limacina, the sea-hare, a gastropod mollusc. He employed Vernon's 

 method for estimating the gases dissolved in sea water, which 

 involves very elaborate apparatus, and gives a fair degree of accuracy, 

 and he estimated the oxygen taken in and carbon dioxide given off. 

 Fig. 123 a taken from his paper shows the curves which he got by 

 plotting the cubic centimetres of oxygen taken in or carbon dioxide 

 given out per kilogram of eggs per hour against the time from laying, 

 all at three different temperatures. It will be seen that the carbon 

 dioxide and the oxygen run closely parallel during the greater part 

 of the time, and that there is a very marked rise in respiratory rate 

 between the 30th and Goth hours. It is not easy to understand why 

 at the lowest temperature this rise should be almost abolished, unless 

 the time taken in development was then so long that it had not 

 begun at the looth hour, by which time the other two curves had 

 long attained a steady level. Nor does the upper curve (30°) agree with 

 such a presentation of the data, for it would be expected to rise much 

 more sharply than the curve at 20°, whereas, on the contrary, it rises 

 more slowly. The respiratory quotients worked out as follows : 



Table 79. 



Respiratory quotient 



Hours State of embryo 10° 20° 30° 



8 i-cell — o-8i — 



12 44-cell — 0-85 — 



13 Beginning of morula ... ... ... — 0-98 102 



20 Morula ... ... ... ... ... — 0-72 — 



25 First segmentations of nutritive blastomeres i-oo 0-90 — 



27 Morulation of nutritive blastomeres ... — 0-90 o-88 



30 Ectoderm nearly surrounds endoderm ... — i-o6 — 



35 Ectoderm completely surrounds endoderm 1-25 0'94 0-92 



50 Half-formed embryo ... ... ... — 1-19 — 



60 Embryo quite formed ... ... ... i-oo i-i2 0-95 



120 Embryo with many cilia ... ... ... 0-71 i-ii — 



150 Embryo with rapid rotatory movement ... — 0-98 0-95 



If the figures for oxygen uptake and carbon dioxide production 



during the 2 hours of an experiment were compared, it was found 



