CONTENTS. 



XI 



Chapter XXVI. MYRIOPODA— conlirvu d. page 



3. The formation of the organs . ... 239 



The nervous system . . ... 239 



The eyes . . . ... 241 



The tracheae . . . ... 243 



The protective glands . . ... 243 



The alimentary canal . . ... 244 



The enteron . . . ... 244 



The stomodaeum and the proctodaeum . . . 246 



The mesodermal structures . ... 246 



The body-cavity, the blood- vascular system, the fat-body, 



and the musculature . . ... 246 



The salivary glands . . ... 251 



The genital organs . . ... 252 



General considerations . .' ... 253 



Literature . . . . ... 257 



Chapter XXVII. IXSECTA. By K. Heider . . . 260 



I. Embryonic development . . ... 260 



1. Oviposition and the structure of the ripe egg . . . 260 



2. Cleavage and the formation of the blastoderm . . . 263 



3. The formation of the embryonic rudiment and the embryonic 



integuments . . ... 268 



A. General view of the germ-band and the germ-envelopes 268 



B. The distinction between the superficial and the im- 



mersed germ-band . . ... 272 



C. The distinction between the invaginated germ-band 



and the germ-band that has been overgrown by the 



membranes . . ... 274 



D. Insects with invaginated germ-band . . . 276 



E. Insects in which the germ-band is overgrown by the 



amniotic fold . . ... 282 



F. Transition forms between the two types of development 



of the germ -band . . . 287 



G. General considerations . ... 289 

 4 Development of the external form of the body . . . 290 



A. Segmentation . . ... 290 



B. Stomodaeum and proctodaeum. Labrum . . 293 



C. Extremities . . ... 295 

 I). Xervous system and tracheal invaginations . . 300 

 E. Transition to the definitive form of body . . 302 



5. Completion of the dorsal part of the embryo and degenera- 

 tion of the embryonic envelopes . . . 302 



A. Involution through the development of a continuous 



dorsal amnion-serosa sac . ... 304 



B. Involution accompanied by dorsal withdrawal of the 



amnion only . . ... 307 



C. Involution accompanied by dorsal withdrawal of the 



serosa and complete separation of the amnion . . 307 



D. Involution accompanied by the amputation of both 



embryonic envelopes 



E. General considerations 



