366 ■ PROF. E. A. MINCHIN ON THE BlllTISH [DeC. 13, 



distal extremity, which in some specimens shows sliglit indications 

 of a lance-head, but more usually does not. These spicules are, as 

 a rule, short, from 70 to 140 /x in length, the greatest thickness 

 about 3 fx ; but they are subject to extraordinary variations in 

 length, which ai'e described in more detail below. 



Variations of the Spictdation. — (1) As regards the relative number 

 of the spicules. In some specimens no examples of the thickened 

 triradiates («, 2) are to be found, or only after much searching ; in 

 others, on the other hand, they are relatively abundant (text- 

 fig. 91, figg. 2fZ-;/', p. 364), and by their presence give a distinct 

 facies to the general spiculation, which might lead at first sight to 

 the impression that the specimen represented a distinct species or 

 variety. The relative numbers of triradiates and quadriradiates 

 are also subject to great variation. 



The lai'ge barbed monaxons are always abundant, and constitute 

 a marked feature of the species. Even moi^e charactei-istic are the 

 small slender monaxons (5, 3), which are usually very abundant ; 

 but in some specimens they are relatively scarce, and require to be 

 searched for carefully. They are also very liable to be broken, by 

 reason of their slender proportions. As pointed out below, through 

 Haeckel having overlooked the monaxons in some specimens, he 

 was led to make two species, pinus and complicata, characterised 

 by their presence and absence respectively. I have nevei-, how- 

 ever, found the small monaxons entirely absent in any specimen 

 I have examined, not even in the specimen identified by Haeckel 

 himself as complicata (text-fig. 92, figg. 3 a-3 m, p. 367), The large 

 tinbnrbed monaxons {b, 2) are usually much less abundant than 

 the other two kinds, but can always, in my experience, be found. 



(2) As regards the form and size of the sjncides. The triradia,te 

 systems vary considerably, both in length and thickness of the 

 rays. Any specimen shows a, considerable range of variations in 

 tliis respect ; but in some specimens the spicules show a tendency 

 to be constantly smaller, in others again constantly larger. The 

 greatest extremes of variation that have come under my notice, as 

 regards length of the rays, are shown by the specimens ISTos. 3 and 9 

 of my list given below. In the former, which was a very small 



Explanation of Text-fig. 92 (opposite). 



Spicules of Leucosolenia complicata. 



Figg. 3 a-'A ill. Specimen from Scarborough in Canon Norman's collection, identified 

 liy Haeckel as Ascandra complicata. a~e, triradiates ; d & e, quadriradiates ; 

 f-i, slender monaxons (absent according to Haeckel), showing distinct traces of 

 barbed heads ; j-l, large barbed monaxons ; m, large monaxon without barb. — 

 Figg. 4 rt-^y. Specimen from North Harbour, Peterhead Beach (British Musexim, 

 Bowerbank Collection, No. 987), showing the remarkable length reached by some 

 of the slender monaxons (d~j) and the small size and relative slenderness of the 

 large barbed mona.\ons {a~c). — Figg. 5 a-5 li. Monaxon spicules of a specimen 

 from the British Museum (Reg. No. 15.1.9.32-34), showing the manner in which 

 some of the slender monaxons {a-d) are not only of gi-eat length but of unusual 

 thickness and curvature. Other monaxons of the slender type are quite normal 

 {e~g). h, one of the largo barbed monaxons. 



