668 THE RESPIRATION AND [pt. hi 



be feared that the number of points secured by Hyman is insufficient 

 to establish so sharply inflected a curve. It gives us little indication 

 concerning the metabolic rate for we do not know the rate at which 

 the non-respiring yolk is disappearing, but Hyman did not hesitate to 

 conclude that " the respiration is probably highest per unit weight of 

 protoplasm early on the second day of development since from that 

 time on the amount of protoplasm increases greatly but the oxygen 

 consumption does not increase in like proportion, in fact, a con- 

 siderable part of the oxygen consumption after the third day is due 

 to the activity of the heart. As the embryo is continually increasing 

 in size after this time while the oxygen consumption per hour shows 

 little increase relatively, we may reasonably conclude that the oxygen 

 consumption per unit weight of the embryo is actually decreasing". 

 Hyman also made estimations of the carbon dioxide production, 

 observing the time required for 40 eggs to take a given amount 

 of sea water from pH 8-2 to 7-6, but these she did not publish, 

 simply stating that "the study of the CO2 production yielded 

 similar results. It increased per unit time up to the early part of the 

 second day of development after which it fell, rising again in later 

 periods". 



A comparison between the results of Hyman on the oxygen con- 

 sumption of Fundulus and Bataillon on the carbon dioxide production 

 of Phonixus is of interest. Bataillon's work was apparently unknown 

 to Hyman, but it can hardly be mere coincidence that the general 

 tenor of the curves should be the same. The first peak in Hyman's 

 curve is on the 2nd day, so is the first peak on Bataillon's curve, the 

 great trough on Bataillon's curve presumably corresponds with the 

 low values obtained by Hyman on the 3rd day, and all the later 

 values show a suggestive though not close correspondence. However, 

 from the description given in each case, there is some doubt as to 

 whether the underlying processes are going on synchronously, and 

 doubtless the time of development in the two minnows differs. It may 

 also be significant that Tangl & Farkas's few points for the carbon 

 dioxide output of the trout egg show a slackening of the rise just at 

 the time of Hyman's first trough. 



The respiration of the plaice egg {Pleuronectes platessa) has been 

 investigated by Dakin & Dakin and by Burfield. Dakin & Dakin 

 made careful analysis of the eggs at two points in their development, 

 at a point between the 8- and i6-cell stages and at 14 days after- 



