SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 659 



calorific quotients thus calculated approach the carbohydrate level 

 rather than any of the others, for, as will appear later, there is much 

 evidence associating a combustion of carbohydrate solely or pre- 

 dominantly with the earliest stages of development. 



4-5. Respiration of Annelid, Nematode, Rotifer, and Mol- 

 luscan Embryos 



Faure-Fremiet, in the course of his researches on the physiology 

 of the egg of the polychaete worm, Sabellaria alveolata, carried 

 out some determinations on the gaseous exchange, although, as far 

 as I can find, his figures are not to be found in the literature in full. 

 Using the Levy-Marboutin technique for estimation of dissolved 

 oxygen in sea water, Faure-Fremiet found that the unfertilised eggs 

 consumed almost as much oxygen as the fertilised ones. Thus 100 gm. 

 of egg consumed in 100 minutes before fertilisation 42 mgm. of 

 oxygen, and afterwards 47 mgm. of oxygen at 20°. At 19° the 

 relative figures were 36 and 38, at 16° 15 and 16, at 11° 13 and 13, 

 and at 0° 8 and 7. The feeble rise in respiratory rate (not more than 

 12 per cent.) appeared, therefore, to fade away as the temperature 

 was lowered, a fact which led Faure-Fremiet to conclude that it 

 was not of essentially the same character as the 800 per cent, rises 

 invariably found in the case of the fertilised echinoderm egg. From 

 these figures he calculated a temperature coefficient which was i-6 

 between o and 10° and 3-2 between 10 and 20°. As regards the rise 

 in respiratory rate on fertilisation, it may, owing to loss in raising 

 the cultures, etc., have been rather higher than the figures actually 

 show. Faure-Fremiet also estimated the liberation of carbon dioxide 

 from these eggs, using a modified form of the Osterhout-Haas method, 

 i.e. titration of sea water in which the eggs have been respiring, to 

 different end points with various indicators. Faure-Fremiet did not 

 publish the figures he obtained by this method, and did not venture to 

 calculate a respiratory quotient from them, but merely stated that 

 "the relation between the values found is always near enough to unity 

 to constitute a verification of the results observed, or at any rate of their 

 order of magnitude". I do not quite understand what this means, but 

 we may conclude that there is some evidence, at any rate, in favour of 

 the respiratory quotient of Sabellaria eggs in the segmentation stages 

 being about i-o. The resemblance between this figure and those 

 obtained for segmenting echinoderm eggs will be evident. 



