METABOLIC GRADIENTS OF VERTEBRATE EMBRYOS. 



53 



velopment of Fundulus heteroclitus. Similar experiments had 

 previously been performed by Scott and Kellicott ('16), but ap- 

 parently no report of these experiments beyond the abstract re- 

 ferred to has ever been published. In this abstract it is stated 

 that during the early stages of Fundulus up through the forma- 

 tion of the embryo the rate of oxygen consumption is less than 

 o.io c.c. per hour per thousand eggs. This statement is in gen- 

 eral true; however, it misses the really fundamental point about 

 the respiratory rate during the early stages. I do know why the 

 marked change which occurs at the time that the germ ring is near 

 the equator of the egg should have missed the attention of these 

 investigators; but at least no mention of this is made in their 

 abstract. They noted a marked increase in rate of oxygen con- 

 sumption when the heart begins to beat ; beyond this time there is 

 no marked rise but a general upward trend with a great increase, 

 after hatching. 



TABLE I. 



RATE OF OXYGEN CONSUMPTION OF THE EGGS OF FUNDULUS HETEROCLITUS 



DURING DEVELOPMENT. 



Results given in cubic centimeters of oxygen consumed per 1000 eggs per 

 two hours in exps. i, 2 and 3 ; per 3 hrs. in no. 4. Temp. 20 C. 



My determinations of the rate of oxygen consumption were 

 made by the same method used by Scott and Kellicott. The 

 carbon-dioxide output was determined by the phenolsulphontha- 

 lein method. Forty eggs of approximately the same stage of 



