STEUCTUEE AND BIOLOGY OP SCHIZONEUEA LANIGEEA, 687 
unable to establisli its presence in the apterous viviparous 
female of S. lanigera. 
E. Tbe Reproductive System (PI. 38^ fig. 5; PI. 41, 
fig. 35; PI. 42, figs. 45, 46). 
The reproductive organs of the apterous viviparous female 
occupy a considerable portion of the body. lu general mor- 
phology they are simple in structure, and resemble in a 
general way those described by earlier investigators, such as 
Dufour (1833), Witlaczil (1882), etc., in other aphids. 
They consist of a number of thin-walled tubes or large 
ovarian caeca, a pair of oviducts, and a stout, muscular 
vagina which leads to the genital orifice, the whole forming 
the ovarium. 
The ovarian caeca (^5. c.) are transversely constricted at 
intervals along- their length, forming a series of several 
ovarian chambers {p. a.), in which the embryos are developed. 
The caeca are developed in two lateral groups of about five 
tubes in each group, and extend over the alimentary tract, 
throughout the body. In the posterior region of the abdo- 
U)en they open into the two oviducts {od.), which pass 
beneath the rectum and unite in the region of the sixth abdo- 
minal segment to form the stout, muscular vagina (^J.), which 
extends beneath the rectum to the genital orifice (y. o.). 
The large ovarian chambers contain embryos in vai-ying 
stag-es of development, those in the chambers nearer the 
genital orifice being more fully developed. In the earlier 
stages of development these embryos were called “ pseud- 
ova.’^ The development of the pseudovum has been described 
by Huxley (1858, p. 215) in an agamic stage of a species of 
Aphis. According to this author, it would appear that the 
embryos are developed from pseudova, which, surrounded by 
a vitelline substance, are set free in the chambers of the 
ovarian cteca, and eventually become changed into cellular 
germs, from which the germ-layers of the embryos are 
developed. 
