A Theory of the Formation of Animals by W. T. Hillier

By W. T. Hillier

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The steepness of t h e pitch of the spiral course of phantoms Blue and Green is probably twice as great as the steepness of the spirals of phantoms Red and Yellow. A reference t o Fig. 24 will show t h a t , while at first there 54 THE FORMATION OF ANIMALS is but little difference in the course of the two spirals, there is in the later stages a great difference. Phantoms Blue and Green design narrow tubes, which are separate from one another, while phantoms Red and Yellow together make the design of a single wide structure —the intestine.

At a greater distance from t h e axis b u t moving in t h e same direction are t h e paths for 3c 2 P aa , 3d 2 P aa . The paths of all the other cells except 2d 222 curve in the opposite direction; 3c2PaP, 3d2PaP have slightly curved paths, so have 3c l a , 3 d 3 a ; more curved are t h e paths of 3c 2 a l , 3d 2 a l , 3c 2a2 , 3d 2a2 , while 3 ^ Ρ , 3dxP have t h e most curved paths of all. I t will be observed t h a t the cells 3c 2 a 2 , 3c 2 a l , 3c l a , 3CXP, are at first placed in t h a t order from front t o back.

At t h e same time the muscular walls of the body and t h e intestine of the worm are forming, the already modified excretory organs are beginning t o be superseded by t h e formation of t h e permanent organs of t h e adult, and t h e nervous system, too, is being elaborated. The two head tentacles begin t o appear, and close t o their bases arises t h e double mass of nervous tissue which becomes t h e supra-cesophageal ganglion of t h e worm and forms a large p a r t of the brain. F r o m it run t h e two large strands t o t h e ventral nerve-cord which, together with t h e ganglion above and their junction with t h e cord below, form a ring of nervous tissue round t h e oesophagus.

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