- 1 Cleavage, at first total, commences before the accumulation of the yolk, and later becomes superficial.
- 2 A blastoderm covering the yolk is formed.
- 3 A germinal band is formed by further division of the blastoderm cells along the ventral surface of the embryo.
- 4 The band terminates anteriorly in a large cap of cells, posteriorly in a similar but smaller cap of cells.
- 5 The anterior cap differentiates into:- (a) the central nervous system; (b) the segmental appendages; (c) the anterior plaque of endoderm.
- 6 The whole development proceeds singularly directly to the definitive form of the larva.
- 7 Coelomic vesicles have not been traced at any stage.
- 8 The genital rudiments differentiate from the inner part of the germinal band posterior to the third pair of walking legs and are solid structures.
- 9 The posterior polar cap proliferates a mass of cells which indents the yolk at its posterior end and is therefore responsible for the morphological aspects of the lateral caeca.
- 10 The posterior mass of cells differentiates dorsally into the mid-gut, or colon, and ventrally into the upper rectum or post-colon. The malpighian tubules arise at the upper end of the post-colon.
- 11 The proctodœal invagination sinks into the posterior mass of cells and is the only part of the hind-gut to be lined with chitin.
- 12 The stomodœum arises between the cheliceral rudiments and does not pierce the central nervous system.
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