DEVELOPMENT t)E ANTEDON (COMATULA, J.AMlv.) KOSACEUS. GST 



attach themselves to tixc-il objects by means of their "accessory rays" (or dorsal cirrhi), 

 and that they extend their ])rin(ipal rays in every direction ; bnt in asserting that this 

 is " ponr atteindre I't pour attu'er la proie vers I'orifiee buccal," he simply hazards a 

 supposition lor which there is not any foundation in fact, the arms not being used 

 for the purpose of grasping food or of conveying it to the mouth. It is obvious that 

 M. DE Blaixville was entirely unacquainted Avith the excellent description of the 

 alimentary canal previously given by Heusij^ger ; and that he stated as fiicts what were 

 only his own conjectures. 



Not many years after Mr. Thompson's publication of his Pentacrinus Eitropa'us, he 

 ascertained that it is nothing else than the young of the Comatuhi, to which he had pre- 

 viously noticed its close resemblance. This discovery he communicated to the lloyal 

 Society in a " Memoir on the Star-Fish of the genus Comatula, demonstrative of the 

 Pentacrinus Euro])ceus being the young of our Indigenous Species"', which was read on 

 the 18th of June 1835, but was not published in tlie Philosophical Transactions. The 

 evidence which he adduces on this point is drawn from the resemblance between the 

 most advanced specimens of Pentacrinus and the youngest Comafuhe, which is so close 

 as to leave no reasonable doubt of the development of the former into the latter. 

 Mr. Thompson' also describes iu this Memoir the development of the ova in conceptacles 

 formed by the thickening of the membranous expansion inside each of the first fifteen 

 or twenty pairs of pinnte. The ova, he says, " make their exit through a round hole on 

 the fascial side of each conceptaculum, still, however, adhering together iu a roundish 

 cluster of about a hundred each ;" and he adds " by what means these ova are disparsed, 

 or how they become attached to the stems and branches of corallines, remain to be dis- 

 covered." He surmised that the parent must be gifted with the power of placing them 

 in appropi'iate situations ; and that from " the dispersed and attached ova " the young 

 Pentacnni at once shoot up, — a supposition which was extremely natural at the period 

 he wrote, not the least suspicion that the first product of the embryonic development 

 of the EcHixoDERMATA generally is an active free-swimming pro-embryo, having at that 

 time been hazarded by any Naturalist. 



In the same year (1835) some important observations on Comatula were published by 

 M. DujAKDiX", wlio liad watched the animal in a living state at Toulon. Like Mr. 

 Thompson, he noticed the development of the ova in the swollen pinnules, and their 

 escape througli apertures which form in the integument. He also stated correctly that 

 these animals habitually live attached to Sea-weeds, Zoophytes, &c. ; only swimming 

 occasionally for the purpose of changing their place of attachment. And he recognized 

 the fact that the arms are not prehensile, and that the food is obtained through an 

 agency altogether distinct from that of which other Star-fish avail themselves ; but of 

 that agency he gave an entirely erroneous account (which he subsequently withdrew), 

 being ignorant of what microscopic examination has since revealed as to the ciliary 



' Edinburgh New Philosophical Journal, vol. xx. (1835-30), p. 29-3. 

 = Llnstitut, Xo. 119 (1835), p. 268. 

 MDCCCLXVI. 5 B 



