664 



THE RESPIRATION AND 



[PT. Ill 



the point marking the close of the great rise is complete sketching 

 out of the embryo with most of its parts. A study of Carazzi's mono- 

 graph on the development of Aplysia does not reveal any more 

 striking correlations. It is worth noting that Buglia's figures for 

 metabolic rate must be accepted with the reservation that we do 

 not yet know how the dry weight of the gastropod eggs varies during 

 their development, nor how the total nitrogen behaves in relation 

 to the total wet and dry weight. It is therefore not possible as yet 

 to say how far Buglia's curves are comparable with those which 

 have already been given for the metabolic rate of echinoderm eggs 

 (i.e. related to so many mgm. of egg nitrogen). Nevertheless, it is 

 interesting that the respiratory rate seems to increase as Aplysia 

 develops, rising between two steady levels, just as that of echino- 

 derms does. Whether these metabolic rates are at all comparable 

 with those for the chick, for instance, is not sure, for in so many 

 cases, e.g. amphibia and fishes, 

 as well as this gastropod, it is \, 

 either not possible or else very |f 

 difficult to measure the actual g - 

 amount of protoplasmic sub- g^ 

 stance at any given moment, 'i^ 

 and the quantities of inert yolk | , 

 must falsify the results a great |: 

 deal. 1, 



Meyerhof continued Buglia's 

 work on Aplysia by making some 

 determinations of its heat-pro- 

 duction at different stages of development. He used the same 

 apparatus as had been employed for his heat-production work on 

 echinoderm eggs, and did oxygen estimations by the Winkler method. 

 The calorific quotient worked out at 2-8 for the early and 2-9 for 

 the late stages. Meyerhof confirmed Buglia's S-shaped curve for 

 respiratory rate in these eggs (see Fig. 123^) and concluded from 

 the calorific quotients that fat was being burned as a source of 

 energy throughout development, pointing out the correspondence 

 between this finding and the richness of the eggs in yolk compared 

 with echinoderms. 



o ^ 



/ o 



o ^y^ 



o 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 

 Hours after fert. 



Fig. 123 b (Meyerhof). 



