1904.] SPONGES OF THE GENUS LEUCOSOLENIA. 383 



the spicviles of L. comjolicata, so tliat the two species wei'e evi- 

 dently growing in close proximity, as so often occurs ; l)nt all 

 of them show, as has been stated, additional spicules. Since 

 L. variabilis forms a dense tangle amongst the seaweeds, li3^<lroids, 

 and other organisms, and might easily be involved in this way 

 with quite distinct calcareous sponges, the idea occurred to me 

 that the spicules in question miglit belong to anothei- sponge ; 

 and on examining cai'efull}^ my specimens of L. variabilis fi'om 

 Roscoft', and picking them ovei' under a lens, 1 was able without 

 difficulty to trace these spicules to their source. Growing on the 

 seaweeds, in closest proximity, very often, to the tubes of the 

 Leucosolenia, were numerous small Sycons, i-anging in size from 

 minute Olynthi to specimens a centimetre or more in height, but 

 all alike showing a characteristic spiculation, which accounted at 

 once foi- the intrusive spicules in my prepaiutions. I have not 

 been able to identify this sponge in Haeckel's monograph, neithei' 

 among the Sycons nor the Leucons. I content myself, therefore, 

 for the pi-esent, witli describing the spiculation, and leave the 

 identification of it to a, future pei'iod, or to othei's. Five classes 

 of spicules can be distinguished: — (1) Dermal triradiates (text- 

 fig. 96, figg. 20 «-20 e, p. 381) tending to be irregulai- in form, often 

 nearly equiangidar ; (2) tubar triradiates {i. e. fi'om the walls of 

 the flagellated chambei's), with long straight unpaii'ed i-ay, and 

 .shorter lateral ravs characteristically curved, the unpaii'ed angle 

 very obtuse (text-fig. 96, figg. •20f-2()j, p. 381); (3) gastral trira- 

 diates and quadriradiates, with long straight unpaired I'ay, shoi-ter 

 paired rays slightly curved, gasti'al ray present oi- absent, unpaired 

 angle nearlv a I'ight angle or less, at any rate consideiubly less than 

 120° (text-fig. 96, figg. 20 7».-20^;, p. 381); (4) quadriradiates 

 from the oscular rim, the thi-ee basal rays neaily equal in length, 

 the unpaired angle neai'ly 180°, so that the sj^icule is nearly 

 T-shaped (text-fig. 96, figg. 20 k, 20 1, p. 381) ; and (5) monaxons of 

 very characteristic form, the proximal half neaiiy sti'aight, taper- 

 ing to a point, the distal half ciu'ving evenly outwards, without 

 any diminution in thickness, to the conspicuous, bluntly pointed 

 lance-head. It is the presence of these monaxons that was so 

 often noticed in my specimens of Leucosolenia, variabilis ; it is 

 probable that such monaxons may often find theii- way even into 

 pure cultures of the Leucosolenia, for if thrown oflT b}' the Sycons 

 and washed about in the water they might easily come to stick to 

 the Leucosole7iia oi' to the seaweed on which it Avas growing. 



(c) General Remarks on the SjMcies. 



Haeckel was the first to recognize the specific distinctions of 

 this sponge and to describe accurately its distinctive chai-actei's, 

 although it was common enough in collections long previous 

 to Haeckel's monograph. Bowerbank, as has been already pointed 

 out, figured this sponge and its spicules under the name L. botry- 

 oides, and again in another place as a new species under the name 



