2O ROIJKKT \V. HKGNIiR. 



The eggs whose egg weights are recorded in the second series 

 (Table II.) were placed in a covered watch glass along with a 

 piece of filter paper which was moistened with a drop or two of 

 water every day. The loss in weight of these twenty-two eggs 

 during embryonic development was not nearly so great as was 

 that of the first series (Table I.), and doubtless represents more 

 closely the state of affairs tinder normal conditions. Twenty of 

 the twenty-two eggs hatched on the fifth day, the usual time for 

 eggs of this beetle. 



Discussion and Conclusions. The belief has been held for many 

 years that eggs diminish in weight during the early embryonic 

 stages, and before extraneous food is consumed. That this belief 

 is well founded has been proved by careful experiments with the 

 eggs of several species of animals. 



Pott and Preyer (1882) have shown that the hen's egg loses 

 weight during incubation. The amount of oxygen absorbed by 

 the eggs equaled the amount of CO 2 excreted. This excretion, 

 produced in the physiological processes taking place during in- 

 cubation, does not, at least in this case, account for the loss in 

 weight, as is usually supposed, since the decrease is equalized by 

 the absorption of oxygen. The conclusion was reached that a 

 gradual evaporation of the albumen caused the loss in weight. 



When hens' eggs are incubated in desiccators the rate of de- 

 velopment is accelerated during the first three days, but later is 

 retarded, and many of the embryos become abnormal or die 

 (F6re, 1894). 



Eggs that develop in water have also been used to determine 

 the loss in weight of developing eggs during development ( Kit ter 

 and Bailey, 1908). Bailey used for his experiments the eggs of 

 the California mud-fish, Funduhis parvipinnis. Starting ten days 

 after ensemination, 93 eggs were weighed at intervals of about 20 

 hours, covering a period of 9 days. Of the 30 weighing:- made, 

 only 10 showed a gain, and this was accounted for l>> the pre-eiiee 

 of dirt upon the eggs. Bailey believes that the "lo>s in weight 

 must have been due to carbon dioxide (CO.,) and organic salts 

 representing the albuminoid loss, which had passed m through 

 the egg-membrane and been washed away in the -e.i-\\.iter." 



A loss of energy also takes place during segmentation, and, in 



