. Chemical embryology. Embryology. SECT. 7] OF EMBRYONIC DEVELOPMENT 989 6. Perhaps it is no coincidence that the respiratory quotient which is found in the early cleavage stages of small marine eggs such as those of the sea-urchin is in the near neighbourhood of unity. Warburg's respiratory quotient of 0-9 for the first 24 hours of the development of Arbacia pustulosa eggs and Shearer's respiratory quotient of 0-95 for Echinus microtuberculatus are relevant here. \ higher figure still was found by Faure-Fremiet, whose results with the eggs of Sabellaria alveolata worked out at a respiratoiy q
. Chemical embryology. Embryology. SECT. 7] OF EMBRYONIC DEVELOPMENT 989 6. Perhaps it is no coincidence that the respiratory quotient which is found in the early cleavage stages of small marine eggs such as those of the sea-urchin is in the near neighbourhood of unity. Warburg's respiratory quotient of 0-9 for the first 24 hours of the development of Arbacia pustulosa eggs and Shearer's respiratory quotient of 0-95 for Echinus microtuberculatus are relevant here. \ higher figure still was found by Faure-Fremiet, whose results with the eggs of Sabellaria alveolata worked out at a respiratoiy quotient of i-o. As indices of the nature of the combustions going on these figures have to be accepted with caution, but it is natural to suppose that a stage which lasts 5 days in the chick may last only a few hours in lower animals which develop faster, so that the time to look for utilisation of carbohydrate might be from fertilisation to the gastrula stage. 7. Then Simon and Susanna Gage fed laying hens on Sudan III and found that, although red yolks were laid, the embryos showed no trace even of a pink colour until the i oth day of incubation. After that time they became rapidly more coloured, until at hatching they were quite red. One would suppose that, in order to be combusted, fat would have to be absorbed into the embryo, and would take the dye with it, as indeed did happen after the loth day. Murray's estimations of fat storage in the embryonic body confirm this (see Fig. 362), and point to an awakening of fat metabolism after the mid-point of incubation. Then Tallarico and Remotti have brought forward evidence showing that the lipase of the yolk increases markedly in activity towards the end of incubation, while the latter worker finds a precise correspondence between proteolytic activity of yolk and intensity of protein combustion at the 8th day of development. 8. The work of Riddle on the yolk and the yolk-sac is interesting in this connection. From the 15th to th
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