OCR Text |
Show 400 PROF. J. A. THOMSON AND MR. W. D. HENDERSON ON [Apr. 10, (c) To C. gracilis May we have referred a colon)- with pinnules in three rows as M a y described, and to the same species we have referred another colony with only one row. This seemed at first unjustifiable till we saw that in the colony with three rows in the majority some polyps only showed two rows, while in the colony with one row in the majority some showed two rows. (d) The total number of pinnules seems to us of more diagnostic importance than the number of rows, but in what we believe to be C. garcice we find in one colony a range from 16-30 pairs. (e) Comparisons of different colonies of the same species show that there is little use attaching much importance to the length and breadth of the bare streak on the tentacles unless one is sure that the forms compared are similarly preserved and in similar states of extension. (/) Cases like that which we have for purposes of convenience called C. garcice, var. inermis, lead us to agree with Prof. Hickson that the mere absence of spicules does not make a new species. Our general conclusion is that further investigation will show that a number of species of Clavularia should be merged in one, and that at present attention should be paid to the ' tout ensemble ' of characters rather than to any single peculiarity when that is of a quantitative nature. These remarks may serve to support our impression that some of the species of Clavularia are in a state of flux, but they may also suggest an inquiry as to the justifiability of adding seven new species to the already lengthy list. The general answer is supplied by the descriptions given; the characters of the new species seem to exclude the possibility of referring them to any of the species known to us from previous memoirs. It may be useful, however, to indicate briefly some of their outstanding features :- C. crosslandi has characteristic exceedingly minute spicules like water-worn sand-grains and they are crowded in eight longitudinal white ridges. C. repens is like the well-defined G. margaritiferce, but has very different spicules-minute capstans and some quadrangular forms with an axial cross. G. pidchra has unusually long polyps, tentacles, and pinnules. C. zanzibarensis has 6-8 rows of wart-like pinnules practically covering the short blunt tentacles, and the colour is peculiar. C. mollis has grouped polyps, thread-like pinnules almost covering the tentacles, and an unusual amount of contraction. C. ]Ktrvula has very unusual tentacles with only 9 pinnules on each side, though certainly mature, as the eggs and embryos show. C. pregnans has short conical pinnules all round the tentacles and a very large genital expansion with embryos. W e may also call special attention to the viviparity readily demonstrable in G. pregnans and also apparent in C. parvula. Very noteworthy in some of the species is the profuse abundance of zoochlorelke. |