Miscellantous. 87 between the meuibrune of the test aud the uiatlreporie plate. Other tubular glauds, situated on the opposite side of the lEsophagus, in the thickness of tlie mesentery itself, open in part with this ex-cretory duct, and in part directly l)eneath the niadreporic plate, the pores of which probablj-give issue to the secreted li(juid. It is to be observed that, by the intermediation of the infundibuliforni space situated below the madreporic plate, the circulatory apparatus and this glandular apparatus communicate with each other, so that an injection driven through the supposed heart may descend again through the sand-canal. In the Sfjutangidie (Amphidetiis), which have been said to have no trace of a heart, I have found a gland exactly similar to that which hitherto has been regarded as the heart in the Echinida. Lastly, I have ascertained, by varied experiments, that the water which fills the cavity of the test of the sea-urchins can only pene-trate them slowly and by endosraose, either through the buccal membrane or through the ambulacral tubes. AVhen sea-urchins have lived for some time in sea-water coloured with aniline, we very regularly find ihe entire oesophagus and the siphon by which it communicates with the point of reflexion of the intestine coloured red. There has consequently been an introduction of water into the intestine by this course, and a possible passage of a part of this water into the general cavity through the walls of the digestive tube. — ComptesBendiiSj'SoveinheT 16, 1874, tome Ixxix. pp. 1128-1132. Enihryoloyy of the Ctenophora. By Alexaxjjer Agassiz. The question of the systematic position of the Ctenophora can now, thanks to the greater knowledge we have of their embryology, be treated more intelligently. The position taken by Vogt, wlio follows Quoy in removing them from the Acalejjhs altogether, and associating them with the Alollusks on account of the apparent bilaterality so strongly developed in some families {Cestum, Bol'ma, aud Merteiisia), seems not untenable. The nature of their relations to Echinoderms, Polyps, aud Acalephs, as well as the general rela-tions of the Ca?leuterata to Echinoderms, may be discussed again, especially as having an important bearing not only on the value of the Coelenterata as a primary division of the animal kingdom, but also on the limits of the Kadiata, and the possible affinities of the Sponges and Coelenterata suggested by Hackel*. A still more im-portant point developed from this embryology is its connexion with the Gastnea theory of Hackelf, for which he claims that it will supplant the type theory, and give us in its place a new system based upon the homology of the embryonic layers and of the primi-tive digestive cavity. Hackel attempts, in his Gastnea theory, to find an explanation for the natural development of species from a purely mechanical cause, and has been bold enough not only to * E. Hackel, ' Die Kalkschwamme,' Berlin, 1872. t E. Hackel, " Die GastrcBa-ThGorie," Jenaische Zeitschrift, ix. 1874.
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