280 EMBRYOLOGY OF INSECTS AND MYRIAPODS 



ovaries or testes. The upper and middle parts remain unchanged during 

 subsequent embiyonic development, but the lower parts fuse to form the 

 definitive oviduct or sperm duct. 



The sequence in the development of Pyrrhocoris on the basis of a 

 12-day developmental period may be stated as follows: During the first 

 day the 2-4:0-cell stage in the primary epithelium is reached. On the 

 second day the lateral plates of the germ band are formed, and the 

 invagination of the band begins. During the third day the inner layer is 

 differentiated, the germ band has attained its greatest length, the amnion 

 is formed, buds of the appendages appear, segmentation of head and body 

 takes place, and the stomodaeum is invaginated. On the fourth day 

 the embryonic envelopes fuse; the proctodaeum forms; the neuroblasts 

 appear; the thoracic appendages become segmented; the embryo shortens; 

 tracheae, Malpighian tubules, anterior mesenteron rudiment, and the 

 gland of the first abdominal segment appear. On the fifth day the 

 posterior mid-gut rudiment and the germ cells become evident. On the 

 sixth day there take place the formation of the commissures of the ventral 

 nerve cord; preparation for blastokinesis ; definitive shortening of the 

 embryo; rupture of embryonic envelopes at the head end; differentiation 

 of musculature, fat bodies, cardioblasts, and genital ridges; enclosure of 

 germ cells in the genital ridges and further differentiation of gonads; 

 anlage of stink glands; completion of blastokinesis, the serosa forming the 

 cephalic part of the temporary dorsal closure, the amnion the dorsal part 

 of the temporary dorsal closure; and the growth dorsad of the laterad 

 edges of the embryo. On the seventh day the serosa sinks into the yolk. 

 On the eighth day the fusion of the head parts, the definitive dorsal 

 closure, specialization of the mouth parts, development of egg tooth, and 

 cephalization of ventral nerve cord take place. 



The red pigment in the eye and on the sides of the body appears on the 

 ninth day. During the next three days completion of claws and mouth 

 parts, the shift of the gonads to their definitive position, and finally the 

 bursting of the chorion and escape of the nymph occur. 



A PoLYCTENiD (Hespewctenes fumarius Westw.) 



This species belongs to the family Polyctenidae which is closely 

 related to the Cimicidae. It occurs in the West Indies where it is para- 

 sitic on bats. The viviparous manner of reproduction and the associated 

 modifications in structure both in the mother and in the offspring render 

 this form very remarkable. The following brief abstract is taken from a 

 paper by Hagan (1931). 



The mature ovum within the ovariole lacks a chorion, for no egg- 

 folUcle cells envelop it. Cleavage is complete, each blastomere lying in 

 the periplasmic region. The process of segmentation seems to be that 



