OLIGONEPHRIDIA 



257 



of the species have a glabrous surface. The anterior end, as with the 

 egg of the sucking lice, is provided with an operculum that bears the 

 micropylar openings, and at the posterior end there is a stigma with a 

 fine canal which nearly or actually 

 penetrates the chorion. 



The Pigeon Louse (Lipeurus 

 haculus L.) 



As with the sucking hce the infec- 

 tion of the eggs of the pigeon louse with 

 symbionts takes place during a late 

 period of oogenesis. The symbionts 

 wander singly from the mycetocytes up 

 the egg tube (ovariole) and thence into 

 a depression at the posterior pole of the 

 egg. With the invagination of the 

 germ band the symbionts are carried 

 more deeply into the yolk (Fig. 181) but 

 without the close association with the 

 germ band characteristic of Pediculus. 

 The germ band and its envelopes are 

 formed as in Pediculus. Yolk cells 

 penetrate the mass of symbionts, the 

 yolk meanwhile having become divided 

 into spherules. At the time the anlage 

 of the mid-gut epithelium makes its 

 appearance, forming in the same way as 

 in Pediculus, the symbiont masses, each 

 with a yolk cell as nucleus, become surrounded by a membrane, thus form- 

 ing mycetocytes. In the male embiyos the mycetocytes migrate through 

 the mid-gut epithelium and into the fat bodies. Ries (1931) failed to find 

 mycetocytes in the fat of female embiyos and therefore assumed that 

 they all pass into the ampullae of the reproductive organs, where they 

 may readily be demonstrated in the young female. Here they are 

 binucleate in contrast to those found in the embryo and the larva. 



Fusion of serosa and amnion before rupture of the membranes, 

 revolution of the embryo, formation of the dorsal organ, and final 

 absorption of this in the yolk take place as with Pediculus. 



The Guinea-pig Louse (Gyropus ovalis N.) 



The development of the guinea-pig louse, as described by Strindberg 

 (1916), resembles in most particulars that of the pigeon louse described 

 by Scholzel (1937). The former, however, in common with Menopon, 

 Trichodectes, and Gliricola, appears to lack symbionts. 



Fig. 181. — Lipeurus. Sagittal sec- 

 tion of germ band, {am) Amnion. 

 (gh) Germ band, {ser) Serosa, (sym) 

 Symbionts. {yc) Yolk cells. [From 

 Ries.) 



