The Development of the Alimentary Canal in Pieris Brassicae and the Endodermal origin of the Malpighian Tubules of Insects

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Abstract
1. The interstitial (imaginal) rings of the insect gut are interpreted as homologous with the lips of the embryonic mouth and anus of Peripatus (i.e. the blastopore lips). 2. The Malpighian tubules of Amphipod Crustacea, Lithobius, Stenopelmatus (Orthoptera), Hepialus (Lepidoptera), Calliphora (Diptera) are all appendages of the posterior end of the mid-gut and endodermal. 3. The Malpighian tubules of Pieris, although hind-gut appendages must be homologous with those of Hepialus. They are composed of three regions, (1) the functional parts of endodermal derivation, (2) the interstitial or imaginal ring which is probably derived from the posterior interstitial ring of the gut, (3) the common duct of proctodaeal origin. 4. The germ-band of the Lepidopterous embryo has a closed blastopore or primitive streak composed of two circular areas, anal and oral, connected by a median strand. The anal and oral blastoporic areas produce the anterior and posterior mesendoderm rudiments. 5. The development of the stomodaeum and proctodaeum shows that the following characteristics may be ascribed to the various parts of the gut.

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