368 PROF. E. A. MINCHIN ON THE BRITISH [DeC. 13, 



colony, the unpaired rays vary from 70-90 fx, the paired rays from 

 65-80 ^i in length (text-fig. 93, figg. 6 a-Q h, p. 369). In the latter 

 (text-fig. 93, figg. 8 «.-8/, p. 369) the unpaired rays vary from 

 120-170 u, the paired from 105-125 /.i. With the increased size 

 the rays also tend to increase in thickness, reaching 10 jw or 

 sliohtly over in their thickest part. This is especially well seen 

 in a specimen sent me by Topsent from Banyuls-sur-Mer, which 

 is remarkable for the general thickness of its triradiates (text- 

 fig. 93, figg. 9 a-9 d, p. 369). It is interesting to note that it is 

 in those two specimens v/ith exceptionally large triradiates that I 

 found barbed monaxons of the largest size, reaching a leng-th of 

 425 f.1 in No. 9 and 360 i^i in Topsent 's specimen, while in No. 3 

 these spicules were below the average in length (1 50-200 ^u) ; the 

 small monaxons, on the other hand, did not show any noteworthy 

 variation in those thi-ee specimens. Topsent's specimen possesses 

 farther interest as being the only example of this sponge which I 

 have seen from the Mediteri'anean. 



The large barbed monaxons {b, 1) show great variations as 

 reo-ards curvature and length, but remain remarkably constant in 

 their general appearance, as well as in thickness. Only in one spe- 

 cimen, No. 4 of my list, have I remarked a tendency to be below the 

 normal in this respect (text-fig. 92, figg. 4 «-4 c, p. 367). In length 

 they may vary from 80 p to nearly half a millimetre, perhaps even 

 more in" sonie cases. The unbarbed large monaxons vary from 

 straio-ht to slightly curved, and may also vary in dimensions. But 

 the greatest %-ariations are shown by the slender monaxons (6, 3). 

 In the first place, while, as a I'ule, they show no trace of a lance- 

 head, in some cases they exhibit very distinctly a rudimentary bai'b 

 at the distal end. This is the case in the specimen in Canon 

 Norman's collection identified by Haeckel as comjMcata, No. 1 of 

 niy list (text-fig. 92, figg. 3/-3 i, p. 367). But the greatest variation 

 is "seen in length. In almost every specimen they vary greatly in 



Explanation of Text-fig. 93 (opposite). 



Spicules of Leucosolenia com-pUcata. 



Figg. 6 a-6 h. Spicules of one of the type specimens of Bowerbank's Leucosolenia 

 '^"contorta (British Museum, Bowerbank's Collection, No. 988, left-hand middle spe- 

 cimen), showing triradiate systems of unusually small size, a &h, triradiates ; 

 c, a quadriradiate ; d & e, slender monaxons showing distinct barbs ; f& g, large 

 barbed monaxons; /;, a large monaxon without barb. — Figg. 7a-7j. Spicules of 

 a specimen in the British Museum (Reg. No. 95.4.6.1) labelled " Leucosolenia 

 hotrjioides " in Bowerbank's handwriting and " type sp." in Carter's handwriting. 

 a & b, ordinary triradiates ; c, a thickened triradiate ; d, an ordinary quadri- 

 radiate ; e, a thickened quadriradiate ; f & g, slender monaxons ; li, a large 

 monaxon without barb; r & J, large barbed monaxons.— Figg. 8 a-8/. Spicules 

 of a specimen in the British Museum (Eeg. No. 95.4.6.2) labelled " Leucosolenia 

 hotryoides " in Bowerbank's handwriting and " type sp." in Carter's handwriting, 

 showing all the spicules above the average in size, a, a triradiate ; I, a quadri- 

 radiate ; ckd, slender monaxons ; e&,f, large barbed monaxons.— Figg. 9 «-9 d. 

 Quadriradiate spicules of a specimen from Banyuls-sur-Mer, sent to me by 

 Topsent, showing the unusually large size and thickness reached by some of the 

 spicules (6 and d). 



