CHAPTER XIX 

 TRICHOPTERA AND LEPIDOPTERA 



TRICHOPTERA 



The Caddis Fly (Neophylax concinnus) 



According to Patten (1884) the somewhat oval eggs of the caddis fly 

 collected from the muddy bottom of a slow-running stream are laid in 

 clumps and surrounded by a gelatinous mass. After a primary epi- 

 thelium (blastoderm) of uniform thickness has been formed, the cells 

 become long and columnar at one pole and correspondingly thinner at 

 the other, the thickened area being the germ disk. Amniotic folds 

 appear on all sides of the embryonic area, gradually extending until they 



am 



Fig. 286. — Neophylax. Sagittal section of germ band, (am) Amnion, {ch) Chorion. 

 (ser) Serosa, (yc) Yolk cell. 



meet nearly over the middle of the germ disk (Figs. 287, 288). The tail 

 fold appears first and grows rapidly (Fig. 286). As development pro- 

 gresses, the amnion (Fig. 288) becomes thinner (Fig. 289), and the germ 

 disk elongates until it extends over two-thirds of the circumference of the 

 egg. Previous to this a gastrular furrow (Fig. 287, gastr) has formed, 

 the lips of which close, cutting off from the surface a median longitudinal 

 band of cells, which on spreading out forms the inner layer (Fig. 289, il). 

 A gastrular tube, however, does not appear. The inner layer soon 

 divides along the median longitudinal line, thus forming a pair of lateral 

 mesodermic bands, each of which at the same time divides into segments 

 or somites. No coelomic cavities are formed. 



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