THE VARIATIONS DURING LIFE 



study the latent period from the metabolic point of view, but unfortun- 

 ately the determinations during the latent period were made at de- 

 creasing temperatures, so that the temperature effect cannot be separated 

 from a " spontaneous " fall in metabolism which may have occurred. 



5. Possible breeding variations in standard metabolism. Krogh 

 [1904] has described variations in the respiratory exchange of the frog 

 corresponding to the seasons and especially to the state of the repro- 

 ductory organs, showing a very large increase during the breeding 

 season. Later experiments (Krogh [1914]) have shown, however, 

 that in this case we have to do only with changes in muscular ac- 

 tivity, as the differences disappear completely when the animals are 

 narcotized. There is, however, a case on record in which a large 

 "spontaneous" increase in standard metabolism is still an eventuality 

 which must be taken into consideration. 



Valenciennes [1841] has described how the female Python, when 

 the eggs are laid, curls up around them covering them completely 

 with her body. The temperature measured between the coils then 

 becomes extremely high, though the animal does not make any 

 movements beyond respiring deeply and frequently. The following 

 temperature observations have been extracted from the paper of 

 Valenciennes : 



TABLE XXX. TEMPERATURE OF A BROODING PYTHON EGGS LAID MAY 6. 

 INCUBATION 56 DAYS. 



On July 2 the eggs were hatched. The mother left them, and 

 her temperature fell to 24 though she took food for the first time since 

 February 2. The writer has had occasion to observe that a Python is 

 especially quiet during the first period of the incubation when the 

 temperature is highest, and it appears unlikely that muscular move- 

 ments should be at all responsible for the large increase in temperature. 

 Respiration experiments on a brooding Python are certainly desirable 

 but not easy to obtain, 



