Identifier: introductiontozo00dave Title: Introduction to zoology; a guide to the study of animals, for the use of secondary schools; Year: 1900 (1900s) Authors: Davenport, Charles Benedict, 1866-1944 Davenport, Gertrude Anna Crotty, 1866- Subjects: Zoology Publisher: New York, Macmillan company London, Macmillian and co., ltd. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: THE EARTHWORM AND ITS ALLIES 139 This group contains several rather rare animals. One of the commonest is Phascolosoma,1 which is a tough but smooth-skinned, cigar-shaped worm, which one can dig up on our sandy beaches (Fig. 125). One end is pointed ; from the other a great proboscis terminating in tentacles surround- ing a mouth can be extruded. Another species found on our beaches after a storm, something like a small cucumber in shape and size, has a row of bristles at each end, indicating its relationship with the bristle-bearing worms. This species, Echiurus,2 is seg- mented when young like Nereis, but eventually it loses its seg- mentation (Fig. 12(>). Several species of Sipimculus are edible, and are held in esteem by the Chinese. To the account of the Oli-gochreta above given may be

Text Appearing After Image: postset added some statements concern- Fm one-half nat. size. Aboutprob., proboscis ; ant. set., anteriorseta;; post, set., posteriorsetjB. After Greef, from Par-ker and Haswells Text-book. ing a group of annelids of verydifferent appearance. The leeches,or blood-suckers, are flattenedAvorms, Avhich, like the earthworm,show metamerism ; that is, there is a repetition of the in-ternal organs. They are also segmented; that is, thebody has external rings, although they may be obscure.One segment does not, hoAvever, as in the earthworm, 1 0d(TKa;\oj, sac ; <rw/xa, body. 2 ex adder ; ot)/>d, tail. 140 ZOOLOGY correspond with one metamere, but there are three, four,or five segments to a metamere. Leeches have no para-podia and no bristles; but they have a sucking disk atthe posterior end of the body for the purpose of adhesion(Fig. 127). They usually have a smaller, anterior suckingdisk around the mouth, which may or may not be providedAvith teeth, for the purpose of cutting

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