222 PROBLEMS OF GENETICS 



enumerated, Tower describes experiments showing, as he believes, 

 that some of them may be caused to appear by applying special 

 treatment to the parents during the "growth and fertilisation" 

 (p. 287) of the eggs. The most striking example is that in which 

 4 males and 4 females of decemlineata were kept very hot (average 

 35 C.) and dry, and at low atmospheric pressure (19-21 inches). 

 The eggs laid were restored to natural conditions. These gave 

 506 larvae, from which emerged 14 normal, 82 pallida and 2 

 "immaculo-ihoraXy" viz., without pigment on the pronotum. 

 The account of the rest of the experiment is somewhat involved, 

 but I understand that the pallida, of which two only survived, 

 behaved as normal recessives when bred to the type: also that 

 the parents, after having laid the eggs whose history has been 

 given, were restored to normal conditions and laid 319 eggs which 

 gave 61 normals. 



In another case normal parents laid 409 eggs in the hot and 

 dry conditions, and on restoration to normal conditions, the 

 same parents laid 840 eggs. Then 409 eggs gave 64 adults as 

 follows : 



Males Females 



decemlineata 12 8 



■pallida 10 13 



immaculothorax 2 3 



albida 9 7 



33 31 



The 840 eggs laid in normal conditions gave 123 normal decem- 

 lineata. 



Similar experiments were made with multitaeniata and gave 

 comparable results, the two recessives (melanothorax, rubicunda) 

 being produced in large numbers when the parents were subjected 

 to heat, but in this case the atmosphere was kept saturated with 

 moisture, instead of dry, as in the previous instance. The same 

 parents transferred to normal conditions gave normals only. 



Lastly the form undecimlineata was exposed "to an extreme 

 stimulus of high temperature, io° C. above the average," and a 

 dry atmosphere, with the result that from 190 eggs there emerged 

 11 beetles, all of the form angustovittata Jacoby, which subse- 

 quently bred true to that type (see p. 295). 



