An easy outline of evolution / Issued for the Rationalist Press Association, Limited.

  • Dennis Hird
Date:
1903
Catalogue details

Licence: In copyright

Credit: An easy outline of evolution / Issued for the Rationalist Press Association, Limited. Source: Wellcome Collection.

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    tube opens into the alimentary canal in the collar region, and projects forward into the proboscis as a support for this organ, which is attached by a very narrow neck to the collar. The whole skin is sensitive, since there is everywhere a layer of nerve-fibrils underlying the outer-skin cells; but this layer is especially thickened along the mid dorsal and mid ventral lines of the trunk, those two regions FIGURE 2. i. Proboscis or tongue. 2. Mouth. 3. Collar. 4. Trunk. 5. Gill slits. being connected by a ring of nervous tissue immediately behind the collar. The dorsal thickening alone is continued into’the collar region, and there it becomes rolled up so as to constitute a short neural tube. There are numerous gill-slit openings into the alimentary canal, in the front part of the trunk; or they may be called pouches, with small outer and large inner openings.
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