. The Cambridge natural history. Zoology. PAXILLOSA 469 unfortunate victims, once inside the stomach, are compelled by suffocation to open sooner or later, when they are digested.^ Many interesting experiments have been made on Astropecten by Preyer and other investigators, but one im- portant fact ^ has escaped their notice, that Astro- pecten, when at rest, lies buried in the sand, whilst the centre of the aboral surface is raised into a cone which projects above the surface. On the sides of this cone the few papulae which this species possesses are distributed. This rais- ing of the aboral


. The Cambridge natural history. Zoology. PAXILLOSA 469 unfortunate victims, once inside the stomach, are compelled by suffocation to open sooner or later, when they are digested.^ Many interesting experiments have been made on Astropecten by Preyer and other investigators, but one im- portant fact ^ has escaped their notice, that Astro- pecten, when at rest, lies buried in the sand, whilst the centre of the aboral surface is raised into a cone which projects above the surface. On the sides of this cone the few papulae which this species possesses are distributed. This rais- ing of the aboral surface is obviously an expedient to facilitate respiration. It loosens the sand over the region of the papulae, and thus allows the water to have access to them. We can thus understand how the restriction of the papulae to the dorsal sur- face, so characteristic of the Paxillosa, is not always as Sladen imagined, a primi- tive characteristic, but often an adaptation to the bur- rowing habits which in all ^la 202 probability are character- istic of the whole order. In both Luidia and Astro- pecten Cuenot has described short spines covered with cilia in. ;adamb. -Oral view of Psilaster acuminatns. X -変 . adavib, Adambulacral spines ; pax, paxillae ; pod, pointed tube-feet devoid of sucker. (After Sladen.) ' Sohiemenz (reference on p. 440 n.). ^ This fact was discovered by Dr. E. J. Allen, Director of the Plymouth Bio- logical Station, who pointed it out to the author during the latter's sojourn at the station in 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 Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company


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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895