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On a Case of Imperfect Development in Echinus esculentus
Author(s) -
Ritchie James,
McIntosh D. C.
Publication year - 1908
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1469-7998.1908.tb07398.x
Subject(s) - ninth , bulge , biology , anatomy , physics , acoustics , astronomy , stars
Summary. The imperfect development of this test of Echinus esculentus is expressed in:—(a) General shape. —Flattened, with a bulge at one portion of the ambitus, and above the bulge a depressed area of the corona. (b) Major symmetries. —The left posterior ambulacrum does not exist after its twenty‐ninth plate (counting from the peristome). The corresponding ocular plate is present, but its shape is unusual and its pore is a mere pin‐hole. (c) Plate details. —On the twenty‐eighth, twenty‐ninth, or thirtieth plate of each of the ten ambulacral rows a series of abnormalities begins, the abnormalities consisting, for the most part, of deficiencies in the number of primitive plates forming a compound plate.Less marked divergencies from the normal can be detected in the sizes of some of the plates and in the irregular courses of certain of the sutures. The stoppage of the growth of the ambulacrum and the plate abnormalities occurred approximately at the same time, and it is suggested that they may be due to functional disturbance caused by some external agent. The distortion of the test subsequent to the arrested development of the ambulacrum has been brought about by a process of regulation. The specimen of Echinus esculentus above described has been deposited in the Royal Scottish Museum, Edinburgh.