636 Gro. W. TANNREUTHER, 
The secondary yolk originates from the follicular nuclei without 
the ego. 
A definite number of parthenogenetic generations are produced 
before the sexual male and female appear. External conditions do - 
not increase or decrease the number of parthenogenetic generations. 
The greatest number of winged forms appear in the second generation, 
especially when the food is abundant. The parthenogenetic developing 
embryo within the winter or sexual egg passes through the winter 
in a half-grown condition. 
A distinct male and female line begins in the fifth partheno- 
genetic generation. The individuals of the presexual or last partheno- 
genetic generation produce either all males or all females. But two 
generations contribute directly to the formation of the male and 
female, i. e., the fifth and presexual generations. 
Material and methods. 
The material upon which this paper is based was collected 
during the summer and fall months of 1903 and 1904. Different 
killing reagents were used with varying degrees of success. Corro- 
sive sublimate, acetic acid mixture, gave the best results. 
Saturated sol. HgCl, in 50°, alcohol 94 volumes 
Glacial acetic acid C. P. 6 s 
The killing fluid was heated to 70°C and poured suddenly over 
the material to be killed. In 5 to 10 minutes the fluid was poured 
oft and replaced by the cool. After killing, the headad part of — 
the thoracic region were removed. 
In case of the egg, they were punctured with a fine needle. 
The material was then dehydrated, cleared in xylol and preserved 
in paraffine. 
The material was sectioned from 6 to 10 w’s thick and stained 
on the slide. The iron-alum haematoxylin stain gave the best 
results. 
Hull Zoological Laboratory, 
The University of Chicago. 
July,-1905. 
