. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. APICAL STRUCTURE IN ABERRANT ECHINOIDS 627 G- 2 6-2 o -m 6 -4. o- n o-i 6 - 5 PLUNGE ANGLE FIGURE 6. Crystal orientations in two tetramerous specimens of Sfr. drobachicnsis. a, #563. b, #57. (In #57, the arrow for plate G-5 has two points because of a 0° plunge.) which, though lacking a genital pore, occvipies a morphologically reasonable position. Apical systems of the two specimens are shown in Figure 6, and the numerical data on their crystal orientations are given at the bottom of Table II. In both specimens, genital pla
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. APICAL STRUCTURE IN ABERRANT ECHINOIDS 627 G- 2 6-2 o -m 6 -4. o- n o-i 6 - 5 PLUNGE ANGLE FIGURE 6. Crystal orientations in two tetramerous specimens of Sfr. drobachicnsis. a, #563. b, #57. (In #57, the arrow for plate G-5 has two points because of a 0° plunge.) which, though lacking a genital pore, occvipies a morphologically reasonable position. Apical systems of the two specimens are shown in Figure 6, and the numerical data on their crystal orientations are given at the bottom of Table II. In both specimens, genital plates 3 and 5 are clearly recognizable from the crystal data. They have azimuths near 90° (plus or minus) and low plunges. The crystal orientations of the other genital plates are reasonable candidates for G-l, G-2, or G-4, although there is considerably more variation in orientation than is encountered in normal specimens. In specimen E-l-57, the plates identified as G-3 and G-5 have no intervening genital plate. Thus, the missing genital plate must be G-4. In specimen Y-l-563, O-IV is evidently the missing ocular. This conclusion is based simply on the fact that there is no ocular plate between the plates that have been identified as G-3 and G-4. In specimen E-l-57, the missing ocular is either O-IV or O-V. The normal crystallography of these two plates is not sufficiently different to enable us to choose between the alternatives. The ocular standing between G-3 and G-5 is broadly insert, suggesting O-V. If this morpho- logical interpretation is correct, the missing ocular is O-IV. Because the morpho- logical development of plates is inevitably distorted to some degree by the tetramerous condition, the interpretation must be somewhat tentative. DISCUSSION It is clear from the data that the morphological inversion in situs inversus specimens is mimicked by a parallel crystallographic inversion. This places the. Please note that these images are extracted from scanned page imag
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
