1904.] SPOKGES OF THE GEXUS LEUCOSOLENIA. 389 



almost exactly upon that of L. variabilis, and every class of 

 spicule found in the one is found also in the other, it is only 

 necessary to enumerate them in the same order as has been done 

 for L. variabilisj and to give at the same time an account of their 

 differences in the two species, and of their variations in the species 

 under consideration. 



(a) Triradiate and Quadriradiate Systems. — (1) The ordinary 

 triradiates (text-fig. 97, figg. 22 «-22 d, p. 388) have exactly the same 

 characters as in variahilis, the unpaired ray short, the unjDaired 

 angle obtuse. They varj- from slender spicules, the v&\& about 

 3 )u in thickness, to thick ones with the rays reaching about 10/.(. 

 There is often a tendency noticeable for the impaired ray to be 

 irregularly cur\ed or bent. This is to be ascribed to the great 

 number of spicules, closely packed in the body- wall of this sponge, 

 ia consequence of which the grooving spicule-rays encounter 

 obstacles to their growth which cause them to be deflected from 

 their normal straightness. (2) The thickened T-shaped triradiates, 

 comparatively few and far between in variabilis, are exceedingly 

 abundant in botryoides, and constitute the most marked feature 

 of the species (text-fig. 97, figg. 22/-22 i, p. 388). They are thick, 

 generally irregularly ciu-ved, with the paired rays usually much 

 longer than the impah'ed one, and when seen from the gastral 

 aspect, if the spicule be lying so that one of the two paired rays 

 and the unpaired ray are in focus at the same time, the other 

 paired ray appears greatly foreshortened, giving the spicule an 

 asymmetrical appearance (text-fig. 97, figg. 22 h, 22 ^, p. 388). 

 (3) The brackets are more abundant than in variabilis and show 

 more tendency to modification and reduction of the unpaired ray 

 (text-fig. 97, figg. 22 I, 22 m, p. 388), so that while in variabilis 

 they might be overlooked, in botryoides they are easily found and 

 recognised. (4) The ordinary quadriradiates are similar to those 

 of variabilis (fig. 22 e). (5) The T-shaped c|uadriradiates are 

 fairly abundant (figg. 22_y, 22 k) and, as in variabilis, the gastral 

 ray is very upright or even inclined backwards in its basal two- 

 thirds. (6) The bi'ackets may develop a gastral ray, which, as 

 described for variabilis, is usually straight and may reach a gi-eat 

 length (figg. 22 n, 22 o). In some specimens this type of spicule 

 is very abundant. 



Explanation of Text-fig. 97 (opposite). 



Spicules of Iieucosolenia hotryoides. 



Figg. 22 a-22 o. Spicules of a specimen from Wembury Baj", PljTnouth. a-d, or- 

 dinary triradiates ; e, a quadriradiate : f-i, thickened T-sbaped triradiates ; 

 _;, h, T-shaped quadriradiates ; I, m, brackets ; n, o, brackets with gastral rays ; 

 p-s, ordinary curved monaxons ; t, u, straight slender mouaxons. — Figg. 23 a- 

 23^. Spicules of a specimen from Berwick Ba}' in Normnn's Collection, identified 

 by Haeckel as AscaUis hotryoides. a, b, ordinarj' triradiates; c, (^, ordinary 

 quadriradiates; e-h, T-shaped triradiates; i, a T-shaped quadriradiate; J-n, 

 ordinary monaxons ; o, p, straight slender monaxons. 



