Ja^i. 4, 1877] 



NATURE 



197 



beyond the compass of our seven or eight octave grand piano- 

 fortes ? This interval is simply the excess of the twelfth power 

 of 3 over the nineteenth power of 2. As powers of 3 are 

 Twelfths, in music — octaves with Fifths, and not merely Fifths 

 — and as octaves are powers of 2, this comma represents B 

 sharp as topping C in its nineteenth octave. Happily any nine- 

 teenth octave is beyond our powers of hearing, even if we adopt 

 a No. I with only one vibration in a second of time. We may 

 therefore dismiss so disagreeable a sound to the so-called "Music 

 of the Spheres," in compliment to Pythagoras, who is supposed 

 to have been acquainted with music of that kind. 



We are too generally prone to rely upon the labours of our 

 predecessors, and hence this peculiar comma has been received 

 without examination, as the overlapping of twelve Fifths over 

 seven octaves, as stated by "A. R. C. After having traced 

 what it really is, wishing to find the author of the miscalculation, 



1 took up a newly-acquired copy of Koch's " Musikalisches 

 Lexicon," which, although written in the last century, is still 

 reputed as a work of authority, and has been re-edited by Arrey 

 von Dommer (8vo, Heidelberg, 1865). I found a more curious 

 mistake : instead of twelve Fifths, it is there stated to be twelve 

 F"ourths or Fifths ; and Koch's way of proving it is by multi- 

 plying the ratios, not as fractions, but as whole numbers. For 

 example, a Fifth and a Fourth we know to make one octave, 

 but Koch multiplies 3 times 3 = 9 in one column, and 4 times 



2 = 8 in the other (p. 24). As the twelve threes are in one 

 column, he arrives by multiplication at the twelfth power of 3, 

 and as the fours and twos are in the other column, he arrives at 

 the nineteenth power of 2. It is desirable that this should be 

 known as a caution against too-ready acquiescence in Koch's 

 calculations. Wm. Chappkll 



On "Comatula (Antedon) Rosacea," and the Family 

 " Comatulidas " 



May I be allowed to point out -to Mr. Stebbing that Co- 

 matula and Antedon are not precisely equivalent names, but that 

 the genus Antedon represents only one of some five or six 

 different types, to all of which ' ' Lamarck's happily appropriate 

 designation Comatula " is equally applicable ; and that this is 

 now generally used as a sort of famdy name, and only when 

 strict scientific accuracy is not very important, as a generic name. 



Johannes Miiller, who laid the foundation of nearly the whole 

 of our present knowledge of the zoology and morphology of the 

 family, was the first to recognise that Lamarck's designation, 

 Comatula included more than one type ; in his well-known 

 memoir, " Ueber die Gattung Comatula, Lamarck, und ihre 

 Arten, " he indicated two distinct varieties of Comatula, the one 

 represented by the ordinary Comatula rosacea, with a central or 

 subcentral mouth, and symmetrically distributed ambulacral 

 furrows ; and another, which he first recognised in the ordi- 

 nary Comatula Solaris, Lamarck, to which he gave the name 

 Actinometra : in this type the mouth is marginal, and the furrows 

 of the ten arms open at equal intervals into a circular furrow 

 running round the edge of the disc, the centre of which is occu- 

 pied by the anal tube. The first of these types is that to which 

 ^^ Freminville's name oi Antedon is now usually applied. Miiller, 

 ^■wever, seems never to have been acquainted with this name, 

 IBd adopted Leach's genus Alecto, which was constituted three 

 years subsequently to Antedon ; while Comatula did not appear 

 till a year later. Recent observations have, however, shown that 



U^cto, as used by Miiller, really includes many forms that are 



le Actinometnr, and the name has passed gradually into dis- 



se, in its original application to the Crinoids ; this was all the 

 more necessary, as the name has been generally received as desig- 



iting a genus established by Lamouroux in 182 1, for a section 



tthe I'olyzoa. 



|MUller was in the habit of using a sort of trinomial nomen- 

 ture in his descriptions of the species of Comatula; thus, 

 *matula {Alecto) europcca, and Comatula {Actinometra') Solaris ; 



"^will probably be advisable to continue this practice, and it is 

 I therefore somewhat unfortunate iha iMr. Norman^ should have 

 transposed Antedon into a masculine name, for de Freminville, who 

 [first proposed it, used it as a feminine one, and described his first 

 land only species as Antedon gorgonia, which is probably the same 

 las Comatula carinata. Lam. Pourtales has already adopted Ante- 

 \don as a feminine name, and we should probably do well to 

 Ifollow his example, especially if we employ Midler's very con- 

 Ivenient system of trinomial nomenclature, for it is far simpler to 

 On the Genera and Species of British Echinodermata," Ann. Mag., 

 IN. H., XVI. 1865. 



write Comatula {Antedon) rosacea, than Comatula rosacea — 

 Antedon ro scums. 



Besides these two types Antedon and Actinometra, there is, as 

 Miiller pointed out, another division of the (7i;wa/«A? represented 

 by the recent Comaster of Agassiz and the fossil Solanocrinus of 

 the Wurtemburg Jurakalk ; these are distinguished from the ordi- 

 nary ComatuUt by the fact that five small basals appear externally 

 between the first radials. The five small ossicles lying between 

 the second radials of Atitcdon Diibenii, Bohlsche, are possibly 

 also external basals. It is unfortunate that Bohlsche was unable 

 to make a further examination of this species, and so determine 

 this very interesting point. 



Miiller considered Solanocrinus, or at any rate .5*. costatus and 

 S.scrobiculatus as generically identical with Comaster, and pointed 

 out that the differences in the form of the " knopf," or centro- 

 dorsal basin, which is elongated and more or less fusiform in 

 Solanocrinus, and hemispherical in Comaster, could not be 

 regarded as of generic value, for similar differences occur 

 among different species of the recent Coma'.ula: ; e.g., between 

 C. Eschrichtii, Miill. and C. phalangium, Miill. I have 

 recently found that such differences may occur within the 

 limits of the same species. Thus, of the two specimens of 

 Comatula {Antedon) macrocnema in the Paris museum, one has 

 a hemispherical centrodorsal basin, just like that of Comatula 

 {Antedon) Eschrichtii,, while in the other it is a short pentagonal 

 or nearly circular column, on which the cirrhi are disposed in 

 four alternating rows, precisely as in Solanocrinus. Go'.te, who 

 has recently made some most beautiful observations upon the 

 embryology of Comatula, opposes the view first suggested by 

 Sir Wyville Thomson, and since adopted and strengthened by 

 Dr. Carpenter, that the centrodorsal basinVepresents a coalesced 

 series of the nodal or cirrhus-bearing stem-joints in the stalked 

 Crinoids, but its condition in Solanocrinus and Antedon macroc- 

 nema seems to show unmistakably that Sir Wyville Thomson's 

 determination of its homologies is the correct one, especially 

 when it is remembered that, as Goldfuss says, young specimens 

 of Solanocrinus are not uncommon, in which the articular sur- 

 faces of the segments composing the elongated "knopf" are 

 visible, although in the adult animal they become so closely 

 united as to be inseparable.' 



Unfortunately we do not know the position of the mouth in 

 Comaster, the only specimen yet known having been dissected by 

 Goldfuss, who says little or nothing about the ventral surface ; 

 but in Phanogenia, a new genus of the free Crinoids established 

 by Loven, it is central, as in Antedon. 



These four types, Antedon, Actinometra, Comaster, ^xA Pha- 

 nogenia, all currently regarded as belonging to Lamarck's genus, 

 Comatula, differ very considerably from one another in many 

 points, perhaps the most characteristic of which is the condition 

 of the basals in the adult animal. 



In Antedon, as shown by Dr. Carpenter, the primitive basals 

 of the Pentacrinoid larva undergo a very remarkable metamor- 

 phosis into the small and relatively insignificant " rosette ; " this 

 is almost entirely inclosed within the circlet of first radials, with 

 which it becomes more or less fused in the adult animal, and by 

 which it is so concealed as very readily to escape notice ; so that 

 all the older investigators either denied the existence of basals at 

 all, or like Goldfuss, mistook the first radials for basals. I have 

 recently found that in Actinometra Solaris (Midler's typical 

 species), and in several other species of the genus, the basals are 

 relatively very large, and take the shape, not of a "rosette," but 

 of a five-pointed star, the rays of which lie on the dorsal aspect 

 of the five sutures of the first radials with one another, while its 

 centre is simply an open and very delicate calcareous network, 

 more or less connected with that proceeding from the inner 

 surface of the radial circlet. These basals are readily exposed 

 by the removal of the flattened centrodorsal basin, the ventral 

 aspect of which exhibits five stellate interradial depressions, into 

 which the basals fit, but they never extend outwards so far as to 

 be visible externally. 



This last condition, of external basals, occurs, however, in 

 Comaster, and in the Jurassic Solanocrinus. The centrodorsal 

 basin of Comaster is hemispherical, and round its ventral margui 

 lie five small triangular basals, not in contact with one another, 

 but so widely separated that the first radials lying between them 



' Further, in the singularly minute Comatula alticeps found by Philippi 



between the valves of a fossil Isocardia cor from the Sicilian Tertiaries, the 



centrodorsal, which he calls the " Welch stuck," is elongated, egg-shaped, 



and visibly composite, bearing at least two, and very probably several more, 



1 alternating rows of cirrhi just like that of Antedon macrocnema. I have 



! little doubt but that this species was a true Antedon, and an ancestor of our 



: recent Antedon rosacea which is now st> common in the Mediterranean. 



