OCR Text |
Show 1882.] PROF. F. J. BELL ON THE COMATULID^E. 531 If science is not to be overwhelmed by literature, an alternative only to be found in such abbreviation as the mathematician, the physicist, and the chemist have already adopted, or in some form of the modern weapon, the cloture. It is unnecessary to insist on the advantage of the former. Recognizing the force of these considerations, I proposed last year to this Society a method of formulating the results attained to, as regards our knowledge of the specific characters of the members of the genus Asterias. For the purpose of extending the process as much as possible, I select on this occasion a different group of the Echinodermata. I cannot pass directly to the subject without expressing my satisfaction with the knowledge that Dr. Vosmaer, of Leyden, has invented a kind of short-hand for the description of Sponges, which will, I hope, bring him before long to a system of formulation. W h e n we make a general survey of the two genera which contain by far the greatest number of the Comatulidae, Antedon and Acti-nometra, we note that, (1) As a general rule, the arms are ten in number or more than ten; the joints before the first division are called radials, those before the second distichals; if there is a further division we shall have palmars ; while the separate joints after the final division are known as the brachials. (2) The leading differences between these sets of joints indifferent species are to be found in the varying arrangement of that mode of union to which Johannes Miiller applied the term syzygial. (3) The cirri on the centrodorsal vary in number, and in the number of their joints. If (1) we use the letters R, D, P for the radials, distichals, and palmars respectively, and insert them in the formula whensoever the respective axillary is a syzygy, we may (2) distinguish which of the first three brachials (one of which is, with but very rare exceptions, a syzygy) is a syzygy by simply making use of the number 1, 2, or 3. Thirdly, the cirri and their number may be thus formulated ; if there are from 1-12 cirri, we may say there are few; if from 12-30, a moderate number; and if more than 30, a large number : if there are not more than 20 joints to the cirri we may look upon them as being few, if from 20-40 moderate, and if more than 40 numerous. I propose to use the letters a, b, and c to represent few, moderate, and numerous respectively ; while the letter for the number of cirri will form the numerator, and that for the number of joints the denominator of a fraction ; and where there is a difficulty of decision one might write ab or be. Antedon and Actinometra may be usefully, though not of necessity, distinguished by making A or A' part of the formula. One or two examples will explain the aim of this note. If we have a ten-rayed Antedon with 15 cirri of 40-50 joints, with its first syzygy on the third brachial, we may write its formula thus, 3 A \ ; so, again, |