536 R. W. Hegner 



Series L.D. /. — Table X 



The above table (Table X) shows the results of a graded series 

 of experiments upon eggs of Leptinotarsa decemlineata centri- 

 fuged from five minutes to two hours and one half. These eggs, 

 including the control (L. D. /, i) all hatched at the same time, 

 showing that the amount of centrifugal force has no perceptible 

 influence upon the rate of development. 



Series L.D. i 



L.D. I. A number of fresh eggs of the potato beetle, Leptino- 

 tarsa decemlineata, were centrifuged at a low rate of speed (360 

 revolutions per minute) for five days. They were oriented with 

 their posterior ends toward the axis of rotation. The resulting 

 embryos (Figs. 22 and 23), which of course would not have 

 hatched, are very similar in appearance to that described under 

 C. M. I, b. The heavy substances in these eggs are apparently 

 non-essential for the development of the embryo, being made up 

 principally of nutritive yolk. When deprived of this material a 

 dwarf embryo is produced at the inner end of the egg. 



Series L.D. 2 



Another batch of potato beetles' eggs were centrifuged at the 

 same rate of speed for seven days. Dwarf embryos developed at 

 the inner light end in every case. No sections were made of these 

 embryos. 



Series L. T. i 



A number of eggs of Lema trilineata were centrifuged with their 

 posterior ends turned inward. In all cases the stratification 

 induced resembles that of the eggs of C. bigsbyana similarly 

 treated. 



Table XI presents the data obtained from a number of experi- 

 ments which have been selected from fifteen series of the eggs of 

 Calligrapha lunata. Eight of these centrifuged eggs produced 

 larvae in the normal hatching period; of these, four were centrifuged 

 with their posterior poles toward the axis of rotation, three with 

 their anterior ends toward the center and one with its side turned 



