. Comparative anatomy. Anatomy, Comparative. C»CUR£NTCR1C STOPOBE. €. EOHINOOCRM. MOJTH F. «MICH0ROATE. CUKXHOPDATZ. KCEPHAaXhORQME. Fig. 3.—Diagrams of embr\-onic stages illustrating the contrast in the fate of the blastopore in different groups of animals. The forms in which the embryonic blastopore becomes the mouth were grouped together by Grobben as PROTEROSTOMIA. The DEUTEROSTOMIA include those animals in which the blastopore becomes the anus or lies in the anal region. The coelenterates, flatworms, annelids, and molluscs are Proterostomians, while echinoderms and chordates are Deuterost
. Comparative anatomy. Anatomy, Comparative. C»CUR£NTCR1C STOPOBE. €. EOHINOOCRM. MOJTH F. «MICH0ROATE. CUKXHOPDATZ. KCEPHAaXhORQME. Fig. 3.—Diagrams of embr\-onic stages illustrating the contrast in the fate of the blastopore in different groups of animals. The forms in which the embryonic blastopore becomes the mouth were grouped together by Grobben as PROTEROSTOMIA. The DEUTEROSTOMIA include those animals in which the blastopore becomes the anus or lies in the anal region. The coelenterates, flatworms, annelids, and molluscs are Proterostomians, while echinoderms and chordates are Deuterostomians. Multicellular animals or Metazoa have bodies which consist of many cells. Grobben, 1908, di\'ides the metazoa into two main subdivisions: I. Proterostomia, in which the embryonic mouth or blastopore persists as the adult mouth. Proterostomians include the Platyhelminthes, Nemathelminthes, Rotifera, Molluscoida, Annelida, Mollusca, and Arthropoda. II. Deuterostomia, in which the blastopore forms the anus or Ues near the anus. The deuterostomians include the remaining groups of animals, —Echinodermata, Hemichordata, Urochordata, Cephalochordata and Vertebrata. Phylum 2. PORIFERA The differentiation among individual cells, which began faintly in certain colonizing protozoa, is carried somewhat further in the sponges, which, though rated as multicellular animals, are hardly more than sHghtly. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Neal, Herbert V. (Herbert Vincent), 1869-1940; Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : P. Blakiston's Son
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