TRICHOPTERA AND LEPIDOPTERA 



343 



depth than elsewhere. At no time and at no part of the germ band is 

 there the shghtest resemblance to the formation of a gastrular tube. 

 Neither is there a proliferation at this time along the middle line, as 

 described by Eastham for Pieris. 



Fig. 301. — Diacrisia. Section through head at stomodaeum (stom). (am) Amnion. 



At 42 hours (Fig. 297C) the two anteriorly directed cephahc pouches 

 so prominent in earlier stages (Figs. 297 A, B) are still present, though 

 they have become smaller and shallower. Just posterior to their dividing 

 wall may be seen a mass of cells of the inner layer which in the middle is 



abdIO 



stom 

 md 



abd9 



Fig. 302. — Diacrisia. Longitudinal section (slightly oblique frontal) of 48-hour 

 embryo, {ab 1-10) Abdominal segments 1 to 10. {am) Amnion, {lb) Labium, {md) 

 Mandible, {mx) Maxilla, {stom) Stomodaeum. {th) Thoracic segments. 



four or five cells thick (Fig. 300 A). Posteriorly, it is continued as a 

 median band a number of cells in width. Two hours later there is 

 anterior to this mass in the head an inner layer one cell in thickness. 

 Neither stomodaeun nor proctodaeum is as yet in evidence. At this 



