SECT. 7] OF EMBRYONIC DEVELOPMENT 973 



computed from the surface law. The result was that the efficiency- 

 rose, giving 



"Ces donnees", said Terroine & Wurmser, "rentrent parmi les plus 

 interessantes actuellement possedes. On ne manquera pas de con- 

 stater qu'une fois prise la precaution d'ecarter la depense d'entretien, 

 si elevee chez un homeotherme, on aboutit a des chiffres tres voisins 

 de ceux de Tangl, Farkas, et Glaser, pour le developpement de I'oeuf." 

 At first sight this correspondence is fallacious, for we are comparing the 

 R.E.E. of the two mammals with the A.E.E. of the various eggs studied. 

 Nevertheless, the calculation given above shows that the basal meta- 

 bolism of the chick embryo is probably many times lower than might 

 be supposed, so that the R.E.E. would differ Httle from the A.E.E. 

 Furthermore, as Terroine & Wurmser point out, the eggs studied are 

 mostly those of poikilothermic animals, whose basal metabolism is 

 known to be very low, and, as for the chick, we know that, for the 

 greater part of its pre-natal life, it behaves as a cold-blooded animal. 

 Rubner's low mammalian values, then, when corrected for basal meta- 

 bolism, would approach the values of Tangl and his associates, and we 

 shall probably not be far wrong if we assess the R.E.E. of all embryos, 

 mammalian as well as non-mammalian, at about 66 per cent. 



The average value of the A.E.E. will presumably vary with varying 

 conditions. Is it affected by temperature ? The only answer to the ques- 

 tion is contained in the papers of Barthelemy & Bonnet, whose experi- 

 ments were conclusive. These investigators, as we have already seen, 

 studied calorimetrically the development of the frog's egg{Ranafusca)up 

 to the disappearance of the external gills, and caused the development 

 to take place at different temperatures. Their results were as follows: 



Efficiency (A.E.E.) 



Time of • Energy in n embryos 



Temperature development ' ' Energy in n eggs 



° C. days ^ a ^ 



9 30 74-78 Average 75 



II 22 71-76 „ 73 



14 20 71-84 ,, 75 



21 8 70-82 „ 75 



