_e._ Formation of the first rudiments of the embryo and of the embryonic membranes 531 Formation of the embryonic membranes 532 The gastrula stage 535 Division of the embryo or primitive band into body-segments 536 Differences between the invaginated and overgrown primitive band 538 Revolution of the embryo where the primitive band is invaginated 540 _f._ Formation of the external form of the body 542 Origin of the body-segments 542 The procephalic lobes 544 Fore-intestine (stomodæum) and hind-intestine (proctodæum), labrum 547 Completion of the head 548 _g._ The appendages 548 The cephalic appendages 548 The thoracic appendages 550 The abdominal appendages 550 Appendages of the first abdominal segment (pleuropodia) 551 Are the abdominal legs of Lepidoptera and phytophagous Hymenoptera true limbs? 552 The tracheæ 553 _h._ Nervous system 554 Completion of the definite form of the body 555 _i._ Dorsal closure and involution of the embryonic membranes 556 _j._ Formation of the germ-layers 558 _k._ Farther development of the mesoderm; formation of the body-cavity 563 _l._ Formation of organs 566 The nervous system 566 Development of the brain 567 Development of the eyes 567 Intestinal canal and glands 569 The salivary glands 570 The urinary tubes 572 The heart 572 The blood-corpuscles 574 Musculature; connective tissue; fat-body 574 The reproductive organs 575 Development of the male germinal glands 579