938 GENERAL METABOLISM [pt. hi 



Clearly the second of these series was in agreement with the law of 

 Terroine & Wurmser, but the first was not. In the first series the 

 higher the temperature the lower the efficiency, i.e. the more the 

 relative amount of combustions and the less the relative amount of 

 storage (although the figures do not show a regular progression). 

 Parallel experiments were made by Gray on the trout embryo, with 

 the following results : 



Gray emphasised these figures, which in his opinion demon- 

 strated that the combustion processes had a higher temperature 

 coefficient than the storage ones, i.e. that development was most 

 efficient at low temperatures, for then storage was carried on to 

 the accompaniment of less combustion. As we have already seen, 

 he used these data to support a particular theory of embryonic 

 growth (see Section 2'6), but it is sure that the problem cannot yet be 

 regarded as settled especially in view of the fact that many researches 

 demonstrate the energetic efficiency to be uninfluenced by tem- 

 perature (cf. the Section on energetics)^. 



The P.E.C. of embryonic growth would seem to be distinctly 

 higher than that of post-embryonic growth. An example could be 

 taken from the work of Farkas and Kellner on the silkworm. On 

 the other hand, if only the early part of development in some 

 organisms be considered the P.E.C. may be still higher. Thus Parnas 

 & Krasinska calculated that as a hatched frog larva might be re- 

 garded as containing 44 per cent, dry solid, of which about 1 2 per 

 cent, would be unused yolk, 32 per cent, would be the dry solid 

 of the embryonic body. Now one frog's egg, according to their data, 

 consumes 27 c.mm. oxygen from fertilisation to hatching, or 0-039 



1 The work of Wood furnishes a suggestion with regard to this discrepancy. He found 

 that trout embryos reared at 7° and 12° gave a P.E.C. of 0-63, which was not far from 

 Gray's figures for 10°. At 3°, however, the P.E.C. was 0-55. In Wood's view, constancy 

 of P.E.C. only occurs within the optimum range of development, and at lower or higher 

 temperatures the processes of combustion and storage are dislocated. But, paradoxically, 

 Wood's final larval size was smaller the lower the temperature ; exactly opposite to the 

 results of Gray. 



