. The microscope and its revelations. les or from six to ten in number,which are arranged with greatregularity around the body is prolonged at its lowerend into a narrow base, whichis furnished with a suctorial the Hydra usually attachesitself by this. while it allows itstendril-like tentacles to floatfreely in the water. The wallof the body is composed of twolayers of cells; and betweenthese, which are the ectodermand endoderm. there is a deli-cate intermediate layer, whichforms the supporting arms are made up of thesame materials as the body :bu
. The microscope and its revelations. les or from six to ten in number,which are arranged with greatregularity around the body is prolonged at its lowerend into a narrow base, whichis furnished with a suctorial the Hydra usually attachesitself by this. while it allows itstendril-like tentacles to floatfreely in the water. The wallof the body is composed of twolayers of cells; and betweenthese, which are the ectodermand endoderm. there is a deli-cate intermediate layer, whichforms the supporting arms are made up of thesame materials as the body :but their surface is beset withlittle wart-like prominences,which, when carefully examined,are found to be composed ofclusters of • thread-cells, havinga single large cell with a longspiculum in the centre of structure of these thread-cells or • iirticating organs willbe described hereafter; at pre-sent it will be enough to pointout that this apparatus, repeatedmany times on each tentacle, isorgan a great prehensile power,. FIG. 658.—Hydra f iiitca, with a young budat b, and a more advam-ed bud at c. to the doubtless intended to the minute filaments forming a rough surface adapted to preventthe object from readily slipping out of the grasp of the arm. whilstthe central spicule or * dart is projected into its substance, probablyconveying into it a poisonous fluid secreted bv a vesicle at its base. 1 On the specific characters of Hi/dm consult Haacke, Ji-nainchi: Zritschr. l:.:!; and Jickdi, /.iiol. Anzcig. v. p. 4!H. • To this intermrdiiitc layer, Mr. G-. C. Bourne applies the term niesof/Jten. For anarc-omit of its variations and structure among the Cu;leiitera, and a discussion of itslimnology with the mesoderm of higher Meta/.oa, see his essay on Fitngin in of the (th-/. Jmirii. Mirtuai-. Sti. HYDROZOA 865 The latter inference is founded upon the oft-repeated observationthat if the living prey seized by the tentacles have a body destitute
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
