Abstract
A FEW weeks ago I dredged, off the north end of Arran, an interesting specimen of Porania pulvillus, Gray (= Goniaster templetoni, Forb.). It is rather more than 5 cm. in diameter, and one of the five short rays (that opposite to the madreporite), when viewed from the aboral surface, is seen to be distinctly bifurcated about 1 cm. from its termination. On examining the oral surface, it is found that the ambulacral groove of the abnormal ray divides into two branches at a distance of 2 cm. from the edge of the mouth. One of these branches runs along one of the forks of the ray to its extremity without further complication, but the other branch, belonging to the second fork, divides again 2 mm. from the first bifurcation, so as to form two tracts, which unite with one another 3 mm. further on, thus inclosing a small piece of the ordinary integument in an ambulacral area. Finally, this ambulacral area divides once more close to the tip of the ray. Consequently, there are three bifurcations of the ambulacral area in a space of not more than 1 cm. in length. As there are no signs of injury or disease on the specimen, the abnormal condition seems to have been caused by a tendency to dichotomous division like that seen in the rays of Crinoids and of the Astrophytidæ.
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HERDMAN, W. An Abnormal Starfish. Nature 34, 596 (1886). https://doi.org/10.1038/034596a0
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DOI: https://doi.org/10.1038/034596a0
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