. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VARIATION IX SAND DOLLARS VARIATION IN PORE-PAIRS IN PETALS 40') The live smallest specimens of each 5-mni. size group from each of the four main series were used for the counting of pore-pairs in the petaloid areas of the ambulacra. The numbers of pore-pairs in all five petals in each specimen were counted. In order to set up a standard for all specimens, it was necessary to determine the distal limits of the petals. Figure 4 shows that there are two rows of pore-pairs in each, starting at the ambulacral plates nearest the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VARIATION IX SAND DOLLARS VARIATION IN PORE-PAIRS IN PETALS 40') The live smallest specimens of each 5-mni. size group from each of the four main series were used for the counting of pore-pairs in the petaloid areas of the ambulacra. The numbers of pore-pairs in all five petals in each specimen were counted. In order to set up a standard for all specimens, it was necessary to determine the distal limits of the petals. Figure 4 shows that there are two rows of pore-pairs in each, starting at the ambulacral plates nearest the apical system. Near the apex these two rows of pores are close together. Gradually these rows. FIGUKE 4. An ambulacral sector of the aboral surface of the sand dollar, Echinarachtiinx panna, showing the arrangement of ambulacral pores in the "petal" of ambulacral area II. The arrows indicate the last pore-pairs to be counted in determining the number of these included in the "; Specimen from Boothbay Harbor, Maine ( X). of pore-pairs spread apart and then toward the periphery they come closer to- gether again, but remain separated. Thus, in the terminology of students of the irregular urchins (cj. Durham, 1955) Echinarachnius has "open ; Beyond the point of this coming together of the rows of pore-pairs, they diverge, and these conspicuous pore-pairs become infrequent. In this investigation counting of pore- pairs has been stopped at the point where the rows start diverging from each other (Fig. 4).. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence,
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
