538 R. W. Hegner 



inward. The age when the eggs were centrifuged ranges from 

 freshly laid to fifty hours. The length of time centrifuged ranges 

 from twenty minutes to twelve hours. It is obvious that there is 

 no definite total amount of centrifugal force which will prevent 

 the hatching of the egg. The orientation of the egg is apparently 

 of no importance. 



The data given in Table XII have been selected from eleven 

 series of experiments upon the eggs of Leptinotarsa decemlineata. 

 There are too few items in this list to warrant any general con- 

 clusions, but the experiments tend to show that an older egg has 

 greater chances of producing a larva after being centrifuged than 

 does one experimented upon a short time after deposition. Both 

 eggs oriented with the posterior end toward the axis of rotation and 

 those with the anterior end toward the center gave rise to normal 

 larvae. 



VIII THE EFFECTS OF CENTRIFUGAL FORCE UPON EGGS LAID BY 

 CENTRIFUGED BEETLES. 



/ ExperiJTients with C. bigsbyaua 



Series C.B. 12 



A female C. bigsbyana was centrifuged at the usual rate of speed 

 for two hours and fifteen minutes with her posterior end toward 

 the axis of rotation. When taken from the machine she seemed to 

 suffer no ill effects but proceeded to walk about and feed as 

 usual. Three days later, July 24, five eggs were laid; two of these 

 were fixed at once and the other three allowed to develop. The 

 former showed no outward signs of any disturbances due to cen- 

 trifugal force. Sections also failed to disclose any rearrangement 

 of materials. The eggs that were left to develop were fixed at the 

 end of eight days. A superficial view of one of these is shown in 

 Fig. 24; a shapeless mass of tissue lies imbedded within the disinte- 

 grated yolk mass. 



Series C.B. 13 



The same beetle as that of Series C. B. 12 laid a second batch of 

 five eggs two hours after the first five were deposited. Two ot 



