OCR Text |
Show 18 PROF. E. A. MINCHIN ON THE [May 2, Clathrina spinosa Minchin, ibid. Leucosolenia spinosa Breitfuss, 1898, Arch. f. Naturges. lxiii. 1, p. 213. (The following references, on the other hand, probably do not relate to the true contorta.) Ascandra contorta Barrois, 1876, Ann. Sci. Nat. (6) iii. Article 11, p. 35, probably refers to Leucosolenia complicata. Leucosolenia contorta Carter, 1880, Midland Naturalist, ii. p. 195. The author remarks that " Bowerbank's illustration of the linear spicule is defective. There are two forms, quite different from each other and from Dr. Bowerbank's figure." I consider it probable from this statement that Carter was dealing with a specimen of Leucosolenia complicata. Ascandra contorta Breitfuss, 1898, Arch. f. Naturges, lxiii. 1, p. 214, refers to a specimen of Leucosolenia complicata; so probably also the sponge described and figured by the same author in Mem. Ac. St. Petersbourg, 1898 (viii.) vi. p. 15, pi. i. fig. 1, and cited by him in other memoirs. And finally it should be mentioned that the numerous specimens sent out from Sinel and Hornell's Zoological Station, Jersey, are all, so far as I have seen, specimens of Leucosolenia complicata. Diagnosis.-Triradiate systems equiangular, with or without gastral rays ; the quadriradiates generally more numerous than the simple triradiates. Rays of the triradiate systems tapering imperceptibly for the proximal half or two-thirds, then narrowing more rapidly to a sharp or moderately blunt point. Gastral rays sometimes short, more usually longer than the basal rays, very slender, sharp, and straight or irregularly curved. Monaxons at least twice as thick as the basal rays of the triradiate systems,-varying in different specimens from a moderate size to gigantic proportions, spindle-shaped, usually slightly curved, and usually with a distinct constriction near the middle of their length ; sometimes very few in number, sometimes absent altogether. The chief objection that can be made, it seems to me, with regard to my treatment of the species, relates to the position of spinosa. Naturalists concerned chiefly with the arrangement of specimens in bottles on shelves will perhaps object to my " lumping" together two forms which can be separated by a definite character, although by one only. Those who reason thus will, no doubt, prefer to retain spinosa as a " species" distinct from contorta ; in that case the type of Bowerbank's contorta belongs to the former species, a fact which raises alarming problems of nomenclature. The range of variation seen in contorta has its natural and logical termination in the form spinosa, and justifies, in my opinion, placing the latter as a synonym. Moreover it is often extremely difficult to be certain that monaxons are really absent in a specimen of " spinosa." They may be so scarce that they have been simply overlooked. After arriving at the above conclusions with regard to the |