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Show 2 0 ON THE SPONGE CLATHRINA CONTORTA. [May 2, a primary monaxon spicule, derived from a single mother-cell, and developing exactly in the same way as a single ray in a tn-radiate system, with which it is strictly homologous. It may be, on the other hand, a secondary monaxon, derived by modification of an entire triradiate system by loss of one ray, perhaps in some cases two rays. Good examples of monaxons undoubtedly of secondary nature are the elbowed monaxons in the stalk of Clathrina lacunosa Johnston (renamed Ascandra angulala by Lendenfeld). I believe also, as stated above, that the monaxons of contorta are to be regarded as secondary. It is clear that a character which is sometimes one thing, in other cases quite another thing, cannot be usefully employed for purposes of systematic classification, not, at least, until more is known about it. If Ascetta spinosa be put as a synonym of Clathrina contorta, it is seen that the species has a wide range, extending from the Adriatic round the coasts of France into the English Channel, and probably also on to the coasts of Great Britain. It is my pleasant duty finally to express my thanks to friends who have assisted me in the preparation of this memoir, put together from observations for the most part of long standing, at a time when the stress of other work, caused by preparations for my departure for the Tropics, was very great. My friend Mr. G. R. Alford, who is making a special study of the variation of this sponge, has given me valuable assistance, as will be evident from the facts I have quoted from him above. Mr. Alford has also kindly undertaken to see this memoir through the press for me. My friend and pupil Mr. L. R. Crawshay has given me great help in preparing the illustrations. Finally, I have to thank Monsieur Topsent, of Caen, for his kindness in sending me specimens from Roscoff and elsewhere and for answering many queries. B ib l io g b a p h y . (1 ) B o w e b b a n k , J. S. A Monograph of the British Spongiadse. London, Ray Society, 3 vols. : 1864-1874. ( 2 ) H a e c k e l , E. Die Kalkschwamme. Berlin, 1872; 3 vols. (3 ) L e n d e n f e l d , R. v. Die Spongia der Adria : I. Die Kalkschwamme. Zeitschr. wiss. Zool. liii. (1891) pp. 185-321, 361-433, pis. viii.-xv. (4) M in c h in . E. A. Sponges in : Lankester, ‘ A Treatise on Zoology/ London, 1900. Other references are cited in the list of synonymy, p. 17 above. E X P L A N A T IO N OF PLATE I. Clathrina contorta from Banyuls. A from above; B from above, and C from the side, to show the oscular tubes (O). |
