SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 649 



the observed and calculated values was even greater if the figures of 

 Meyerhof for heat production were used, and somewhat less if those of 

 Rogers & Cole were substituted for them, but in no case did the results 

 of the two methods coincide, the difference being at least 40 gm. cal. 

 These facts led Rapkine to the conclusion that in this early period 

 simple combustion was to a great extent complicated by coupled 

 reactions, one member of which was endothermic. He saw in the low 

 calorific quotients of Meyerhof and the preUminary heat absorption 

 phase of Bohr & Hasselbalch still further indications that such 

 processes might be by no means negligible. 



4-4. Heat-production and Calorific Quotients of Echinoderm 

 Embryos 



The work on the heat-production of echinoderm eggs divides itself 

 roughly into the long papers of Meyerhof in 191 1, the work of Shearer 

 in 1922, and of Rogers & Cole in 1925. Meyerhof made use of a 

 simple apparatus consisting of a Dewar flask immersed in an accurate 

 thermostat together with a Beckmann thermometer, giving readings 

 correct to -001°. With this apparatus he made many experiments 

 on the production of heat by the developing sea-urchin embryos. 

 One of his typical results was as follows : 



Heat produced in gm. 



cal. per hour per 

 amount of .S" rongylocen- 

 trotus lividus eggs corre- 

 sponding to 1 40 mgm. 

 nitrogen 

 Eggs before fertilisation ... ... ... o-Sg-o-gi 



1st hour after fertilisation ... ... 4-0 -4-2 



2nd hour (transition to 2-cell) ... ... 4-5 -5-0 



3rd hour (4-cell stage) ... ... ... 5-3 -5-8 



4th hour (8-cell stage) ... ... ... 6-o -6-5 



5th hour (16- to 32-cell stages) ... ... 7-8 -9-5 



6th hour (32- to 64-cell stages) ... ... 9-8 



14th hour (larvae begin to swim) ... 12-9 



1 8th hour 17-8 



Another of his experiments is shown in Fig. ii6, taken from his 

 paper. It is interesting to note that, like the curve of Gray for the 

 oxygen consumption of echinoderm eggs, it shows no variations from 

 its smooth course corresponding to the periods of cleavage. During 

 the first 18 hours, the heat-production rate increases by four times, 

 i.e. fairly parallel with the oxygen uptake rate. Membrane formation 

 did not seem to have any effect on the heat-production, for eggs 

 which had stood so long in sea water that they had lost the power 



