A NEW EUROPEAN OK IX OH). By Austin Hobart Clark, Assistant Curator, Division of Marine Invertebrates, U, S. National Museum. The careful and painstaking work of the late Dr. Oswald Seeliger upon the embryogeny of Antedon carried on at Trieste gave results which were, in many important particulars, different from those attained by Prof. Jules Barrois at Villafranca and by Mr. II. Bury at Naples. Seeliger finds the diameter of the eggs to be 0.25 mm., while Bury gives it as 0.30 mm. It will be remembered that Wyville Thomson found the eggs of Antedon bifida to measure 0.50 mm. in diameter. Seeliger noticed that the segmentation from the third cleavage furrow onward was unequal, resulting in the formation of a blastosphere with markedly larger cells at the vegetative' than at the animal pole, but Bury and Barrois found the cells of the blasto-sphere to be similar throughout. Gastrulation occurred, according to Seeliger, scarcely seven hours after the appearance of the first cleavage furrow; but Barrois and Bury first noticed it from twenty to twenty-four hours after fertilization. Seeliger reports that the blastopore is closed at the latest thirty-six hours after the first cleavage, but Bury records that this change takes place about forty hours after. Bury, who was the first to find underbasals in Antedon (though their occurrence in the larvae had been shown to be probable many years before by Wachsmuth and Springer), gives the usual number as three; Seeliger, on the other baud, reports it as four or live. Now from an embryological point of view these differences are fundamental, and are far greater than would reasonably be expected within the limits of a single species. All three workers referred their specimens to Antedon rosa d a , which, as understood by them, ranged from Norway southward to and throughout the Mediterranean; but they all suspected that this specific determination was unsatisfactory, though none of them attempted to investigate the question. The ChalleiKjtr report upon the comatulids had just been published, and this was naturally taken as their systematic hasis. In the preparation of a monograph upon the recent crinoids 1 have been enabled, thanks to the kindness of very many fellow-workers, Proceedings U. S. National Museum, Vol. 38— No. 1749. 329
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