OLIGONEPHRIDIA 



251 



absorbed. The inner entodermal tube derived from the vesicles now 

 undergoes disintegration, leaving as the definitive mid-gut epithelium 

 {mge) the cells originating from the middle entodermal mass. 



Since the nutritive mass is so small in this viviparous psocid, addi- 

 tional food material is obtained through a pseudovitellus in a manner 



eni.ves 



mge 



stom 



mes 





Fig. 172. — Archipsocus. Sagittal section of anterior part of mid-gut enclosing inner 

 entodermal vesicle {ent. ves) at anterior end. (br) Brain, (mes) Mesoderm, (mge) 

 Definitive mid-gut epithelium, {nc) Nerve cord, (stom) Stomodaeum. 



similar to viviparous (ovoviviparous) aphids. Fine cytoplasmic proc- 

 esses pass from the cells of the serosa into the walls of the ovarian tubule 

 wherever the embryo comes in contact with it. In the posterior region 

 the wall of the ovarian tubule is unusually thick, the boundary between 

 it and the serosa (Fig. 173, ser. ovt) being obliterated. It is here that 



proct 



ser.ovt 



Fig. 173. — Archipsocus. Sagittal section showing connection between serosa and 

 ovariole {ser. ovt) at the posterior region of the embryo, (ovt) Ovariole. {p) Thoracic leg. 

 (proct) Proctodaeum. (ser) Serosa, (ser. ovt) Fusion of serosa and ovariole. (y) Yolk. 



on the embryonal side the nutritive mass is continuous with the serosa, 

 thus establishing a means for the embryo to obtain nutriment from the 

 ovarian tubule, A somewhat similar connection is found in the anterior 

 region just in front of the brain. This connection is temporary. When 

 amnion and serosa disappear and the definitive dorsal ectoderm develops, 

 the embryo is disconnected from the maternal wall. The embryo then 



