206 -ENDEAVOUE" SCIENTIFIC EESULTS. 



and those which remain will be characterised by the posses- 

 sion of auxiliary megascleres which are almost invariably 

 stylote. It may be questionable whether the retention within 

 the genus of species with diactinal auxiliaries is strictly 

 proper, but so far as I know, there is no urgent reason for 

 their removal, provided that they satisfy the definition in other 

 respects. 1 Allowance must be made also for the fact that 

 many so-called diactinal spicules are only apparentlv diactinal. 



The distribution of the auxiliary megascleres is subject to 

 a certain amount of variation. In general, they are scattered 

 \\ithout apparent order through the soft tissues, increase 

 in abundance in the more superficial layers, and are some- 

 times so crowded at the surface — though possibly never with 

 any distinct regularity of arrangement — that there results in 

 consequence a definite dermal skeleton. It must be allowed, 

 however, that in particular cases, the auxiliary megascleres 

 may play an appreciable part in the formation of the spicular 

 axis of the fibres, or may actually, as in C. inanchorata, R. 

 and D.,2 become almost or even quite entireh- restricted to an 

 intra-fibral situation. An instance of such invasion of the 

 fibres by auxiliary megascleres is probably afforded by the 

 genus Echinochalimi, some species of which, e.g., E. glabra. 



1 Hentschel (Fauna Siidwest-Australiens. Bd. iii., 1911) has recently 

 without sufficient justification, placed such a species in the genus 

 Spanioploii. 



2 I have examined the specimen recorded by Whitelegge tinder the 

 name of Clathrin itianchornta, R. and D. (Austr. Mus. Mem., iv., 10, 1907, 

 p. 495), and althou§rh the dimensions of the spicules do not agree with 

 the "Challenger" description I cannot do otherwise than agree with 

 Whitelegge in regarding them as genuine examples of the species. Not 

 only do they agree perfectly with the "Challenger" specimen in external 

 appearance, but also in regard to the shape of the acanthostyles and 

 the fsmaller) toxa. I believe, therefore, that we have in the case of this 

 species an instance of one of the very few inaccuracies to be found in 

 the descriptions of the "Challenger" Monaxonida. The spicules within 

 the fibres (the main fibres only) are of two kinds, viz.: (i.) Stouter,, 

 usually curved styli; the stoutest are 24-25 ji in diameter, and their 

 maximum length varies in the different specimens from 480 to 560 p ; and 

 (ii.) slenderer straight subtylostyli (or tylostyli^ probably never of 

 greater size than 450 x 13 ji. These spicules I regard as representing 

 respectively the principal and atixiliary stylotes of other species. Both 

 kinds are basally tipped with a very minute spination which is more 

 conspicuous in the auxiliary spicules. Neither principal nor auxiliary 

 spicules appear ever to occur scattered between the fibres, though the 

 former — but rarely or never the latter— occur abundantly as exteriorly 

 directed echinating spicules, along with acanthostyles, on the super- 

 ficial transverse fibres. The acanthostyles are extremely variable in size. 

 The smallest may be less than 60 p long : but it is impossible to attach 

 any jjrecise upper limit to their length. The greater number by far are 

 less than 200 )i long, and of the remainder the majority are less than 

 240 p; but as the length increases the spicule becomes curved and more 

 and more free from spines and gradually passes into the form of the 

 principal styli. Thus the echinating spicules show a complete transition 

 from accessory spined to princijwil smooth spicules. The toxa are of two, 

 kinds: one. similar in form to that figured in the "Challenger" Eeport. 

 ranges in length from less than 20 p to about 120 p and reaches a 

 diameter of 4 p ; the other is very long and slender, with straight arms 

 inclined at a small angle, and reaches a length, in some cases, of 560 p. 

 with a diameter of about 2 p. Chelte have not been observed, (^^idc 

 remarks on C. cnektto.) 



