Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Dept. of Zoology, British Museum (Natural History).

  • British Museum (Natural History). Department of Zoology.
Date:
1910
Catalogue details

Licence: In copyright

Credit: Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Dept. of Zoology, British Museum (Natural History). Source: Wellcome Collection.

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    which, in the case of the body, are termed body-segments or “ somites.’' A study of the various modifications of structure presented by Wall- Crust acea and other Arthropoda has led to the conclusion that g they are to be regarded as built up of a series of somites or body- segments, which may be distinct or soldered together, and each of which bears typically a single pair of limbs or appendages. Thus, in the Lobster (Fig. 1), the hinder half of the body (or abdomen) is plainly made up of six somites (besides a tail-piece or The Common Lobster (Homarus gammarus). Female, from the side. [Wall-case No. 1.] f telson ”), each of which carries on the under side a pair of “ swimmerets.” The front half of the body is not so divided, but is covered by a large shield or “ carapace ” which projects between the eyes as a toothed beak or “ rostrum.” Since, however, this part of the body also bears a number of appendages constructed on the same plan as the swimmerets of the abdomen, it is con- cluded that here also we have to do with a series of somites, although they are so completely fused together as to be indistin- guishable except by their appendages. That this conclusion is correct is proved by comparison with some of the lower Crustacea, for instance, Anaspides (see Table-case No. 5), in which there is no