1904.] SrONGES OF THE GENUS LEUCOSOLENIA. 391 



(b) Monaxon Spicules. — (1) The ordinary curved, barbed forms 

 (text-fig. 97, figg. 22 j»-22 s, p. 388) have the same characters as in 

 variabilis ; but they are usually short (60 ju-80 jx in length), and 

 though they may vary in size, they never reach quite the length 

 which they do in variabilis ; I have found none exceeding 

 300 ;u in length, and such dimensions are quite exceptional 

 (text-fig. 98, fig. 26 g, p. 390). Further, they have a tendency to 

 be less curved and slightly thicker, in proportion to their length, 

 than in variabilis, and not to dwindle so much in thickness 

 just below the lance-head as do the monaxons of the latter 

 species ; the features desciibed are most marked in specimens 

 in which the monaxons are for the most part short (fig. 22). The 

 monaxons are always abundant and never absent, not even in the 

 specimens identified by Haeckel as Ascaltis botryoides (fig. 23), in 

 which, therefore, they are supposed to be wanting. (2) The 

 slender, straight, refringent monaxons are always present and 

 have the same charactei'S as in Z. variahilis (figg. 22 i, 22 u). 

 (3) The bayonet-shaped monaxons are not to be found in most 

 specimens, but in some they are fairly common (figg. 25 i, 25j), 

 and show the same features as in L. variabilis. 



(c) General Bemarks on the Species. 



Since this sponge was first named by Ellis and Solander in 

 1786, it was for many years the species to which all British Leuco- 

 solenias were referred, both in works dealing with sponges and 

 in the labels of museums and collections, until Haeckel in 1872 

 first pointed out the distinctive characters of the species and gave 

 a diagnosis of it. Haeckel, however, as has been pointed out, 

 wi^ongly separated this species into two, one with, the other with- 

 out monaxons, so that the characters which he ascribed to his 

 unnecessary species botrys are those which should be given to 

 hotryoicles. It is incomprehensible to me how Haeckel came to 



Explanation of Text-fig. 98 (opposite). 



Spicules of I.eacosolenia hotryoides. 



Pigg. 24!a-24ii. Spicules of a specimen from Portrush in Norman's Collection 

 identified as Ascandra botrys by Haeckel. a, ordinary triradiate ; b, ordinary 

 quadriradiate ; c, d, T-sliaped triradiates ; e-h, cm-ved monaxons ; i, straight 

 slender monaxon. — Figg. 25 a-25.;. Spicules of a specimen from Heligoland in 

 the Berlin Museum (No. 1777), showing the bayonet-like monaxons. «, tri- 

 radiate, rather unusually slender; b, T-shaped triradiate; c, d, brackets; 

 e, straight slender monaxon ; f-h, curved monaxons, reaching a considerable 

 length; -ij^/, bayonet-like monaxons. — Figg. 26«.-26Z. Spicules of a specimen 

 from Liverpool in the Berlin Museum (No. 1763). showing the monaxons of 

 great length, a, b, ordinary triradiates ; c, quadriradiate ; d, T-shaped triradiate ; 

 Cj/j brackets ; ^-fc, ordinary curved monaxons; Z, bracket with gastral ray. — 

 Figg. 27 a-27 ff. Spicules of a specimen in the British Museum (Bowerbank Coll.. 

 992), figured in Bowerbank, Brit. Spong. i. fig. 348 (see p. 164;). a, ordinary 

 triradiate ; b, ordinary quadriradiate ; c, T-shaped triradiate ; d, e, ordinary 

 uionaxous ; f, ij, refringent monaxons. 



