2O2 T. H. MORGAN. 



the gall that are all of one size, and give rise to the individuals 

 of the second generation, which, developing wings in most spe- 

 cies, ultimately leave the gall. These migrants contain two kinds 

 of eggs, larger eggs that give rise to females, and smaller eggs 

 that give rise to males. The eggs are deposited upon the bark 



' 



FIG. I. Phvlloxcra globosum. Polar spindles of male and female eggs. The 

 first figure (to the left) is from a large female egg; the second, from a small male 

 egg ; the third and fourth figures are from eggs whose size was not determined. 



of the hickory. From them the male and female individuals are 

 hatched. These soon pair and the female lays her single, large, 

 winter egg on the bark of the tree. This egg hatches in the 

 following spring, and produces the stem-mother. 



A few species have a somewhat different cycle, and in one of 

 them the male and the female eggs are laid within the gall itself. 

 Owing to this condition a large number of the eggs in all stages 

 of development can readily be collected. I have been fortunate 

 enough to obtain a species of this sort, viz., Phylloxera sp. ? and 

 have obtained an abundance of developing male and female eggs. 

 The life history of a species of this sort according to Pergande is 

 as follows : The stem-mother lays eggs that give rise to a genera- 

 tion of wingless forms corresponding to the winged migrants of 

 other species. These wingless individuals contain large and small 

 eggs which they deposit within the gall. From these eggs the 

 minute males and females emerge. In a few cases a winged in- 

 dividual a migrant --is found with the wingless individuals. 

 It seems probable that the wingless condition is the secondary 

 one, hence the occasional appearance of winged forms. 



The Male and the Female Eggs of the Migrants. The eggs 

 are mature in the migrant before it leaves the gall, and the 

 polar spindle is present. It is a difficult matter to find the 

 spindle, and the chance is also small of getting one cut parallel 

 to its equatorial plate. Nevertheless, I have found a fair num- 



