. Contributions to the natural history of the United States of America. Zoology; Chelonia (Genus); Ctenophora; Cnidaria; Animals. Chap. II. HOMOLOGICAL RELATIONS. 71 Fiij. 6. ence consisting in the greater complication of the ambulacral system of the Encope, and in the presence of five ambuLicra, whereas Aurelia has only four. But when it is remembered how simple the ambulacra of Synapta are, and how great a diver- sity exists in the relative development of the ambulacral and interambulacral zones, throughout the type of the Radiates, such differences cannot be considered as impairing the homo
. Contributions to the natural history of the United States of America. Zoology; Chelonia (Genus); Ctenophora; Cnidaria; Animals. Chap. II. HOMOLOGICAL RELATIONS. 71 Fiij. 6. ence consisting in the greater complication of the ambulacral system of the Encope, and in the presence of five ambuLicra, whereas Aurelia has only four. But when it is remembered how simple the ambulacra of Synapta are, and how great a diver- sity exists in the relative development of the ambulacral and interambulacral zones, throughout the type of the Radiates, such differences cannot be considered as impairing the homology of these parts. A further comparison with Melitta quinquefora, Fi(/. 6, will only confirm these conclusions, and, I trust, also go far to show how little foundation there is for a typical separation of the Coelenterata and Echinodermata. In this figure the ambulacral and interambulacral systems are seen from the inside of the lower floor of the spherosome, I, II, III, IV, and V rejjresenting the ambulacral sys- tem, and A, B, C, D, and E the inter- ambulacral system of radiating tubes, and a and b, and 1 and 2, for their respective ambulacral and interambula- cral zones, the branches by which they anastomose with one another. There is, in this genus, as well as in the genera Dendraster and Echinarachnius, Ftff. 3, an additional point of correspondence with Aurelia, not observed in EncojDe: in the interambulacral zones may be seen two simple tubes {1 and 2) bordering ujion the wider pouches, facing A, B, C, D, and E, into which the sexual organs extend. The inninnerable lacunte in the peripheric portion of the spherosome are only dilatations of the radiating tubes, and might at first sight appear to have little resemblance to the chymiferous tubes of the Acalephs; but if, instead of comparing the mode of ramification and the combinations of these lacunse with the ramifications of the chymiferous system of Aurelia, we turn to Polyclonia, as represented PI. XIII. Fiff. 2, or
Size: 1542px × 1621px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdeca, booksubjectanimals, booksubjectzoology
