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Show ] PROF. F. J. BELL ON THE TEMNOPLEURID.E. 437 in other points they are almost exactly alike. Is it possible that they are different sex-forms of the same species ? 3. AMBLYPNEUSTES FORMOSUS. Capt. Hutton states (Trans. New-Zealand Inst. ix. p. 3^2) that his E. elevatus (Catal. N.-Z. Echinodermata, p. 11) is synonymous with this species. There are, as is well known, a number of specimens of this species to which it is easy enough to allot their place, and the only difficulties which arise are those which are consequent on the close affinity of the species A. pallidus. What is of especial interest to note is that here, just as in the forms united under the head of A. griseus, there are two very distinct sizes of the genital pores; the distinction is obvious enough when a iew specimens are carefully observed; but there is no great difference in the moderately-sized madreporic plate, nor can I arrive at any definite correlation of differences in proportion, similar to those already noticed in A. griseus. It is to be hoped that naturalists, who are enabled to get their specimens fresh, will be able to discover with what difference, if any, in the characters of the genital organs this difference is connected. I have been anxious to find some means of expressing this difference :-first, for the purpose of affording a standard to those who are also working at this subject; and, secondly, for the purpose of presenting the difference in relations distinctly to the minds of those who take a less special interest in the matter. By the kindness of a colleague I was provided with four entomological pins of different sizes; the most delicate was almost exactly half the diameter of the strongest; their numbers, for which neither he nor I are responsible, are respectively 2, 1 7, 14, 16. No. 2 is the most delicate, and no. 14 is thicker than no. 17 ; and no. 16 is the thickest, and is rather more delicate than an ordinary toilet-pin. i. A specimen measuring 34*5 millims. in diameter just allowed the insertion of pin 16 into one of the genital pores. ii. A specimen measuring 35*1 millims. in diameter was injured by pin 17. iii. A specimen measuring 28 millims. would only admit the tip of pin 2. iv. A specimen measuring 20*5 millims. easily admitted pin 17, and just refused 14. v. A specimen measuring 21 millims. only admitted just the tip of pin 2. Two series are therefore quite evident. Prof. A. Agassiz has directed attention by his figures to the depressed and oviform varieties of the test; the succeeding Table illustrates this well enough, as it shows that the height may be only 84*1 or as much as 102 per cent, of the diameter of the test; the three other specimens present, however, a very striking similarity in proportion. 29* |