86 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus Cladorhiza, M. Sars (Pis. XX., XXL). 



1872. Cladorhiza, M. Sars, Eemarkable Forms of Animal Life from the great deeps off the 

 Norwegian Coast, pt. i. p. 65. 



Sponge of varying, but usually symmetrical external form. Skeleton usually 

 consisting of a central, erect axis of spiculo-fibre, which may or may not be branched, 

 and from which arise longer or shorter processes also composed of spiculo-fibre. 

 Spicules. — (a) Megasclera ; chiefly stylote and often attaining a great length. (b) 

 Microsclera ; auisochelse, characteristically with three or more claw -like teeth at each 

 end and with a curved shaft expanded laterally into wing-like processes, which are 

 especially developed near the larger end of the spicule. Sigmata may be present. 



The genus was first characterised as follows : — " Spongia sUicea ramosa, fasciculis 

 densis spiculorum acuformium axem soHdam formantibus sustentata, radiculis numerosis 

 arborescentibus ex spiculis ejusdem generis formatis in limo afiixa. Parenchyma axem 

 interuam corticis instar circumdans spiculis superficialibus anchoratis et bihamatis 

 ornatum. Oscula et pori nulla. Ova in apicibus dUatatis ramorum se evolventia " 

 (Sars, loc. cit.). This diagnosis, drawn up for but a single species, may now be emended 

 as above. 



Schmidt ^ includes in the genus also those forms which have isochelate microsclera. 

 It has, however, seemed preferable to us to retain the name Chondrocladia, origin- 

 ally proposed by Wyville Thomson for his Chondrocladia virgata, for the species with 

 isochelaB, and to confine the name Cladorhiza to those with anisochelate microsclera. 

 The two genera thus distinguished are undoubtedly very closely allied, as may be seen 

 by the arrangement and form of the spicules. 



Although the cliS"erent species of Cladorhiza vary very much in external form, yet 

 the difi"erent modifications of the main skeleton, ujaon which the external form of the 

 sponge depends, are easily derivable from one common primary type, and afi'ord inter- 

 esting instances of adaptation. 



In its simplest condition the main skeleton consists of a straight, slender axis of 

 spiculo-fibre, from which short spicular processes (or pinnae) proceed in all du-ections. 

 Cladorhiza ahyssicola, var. rectangular is, nobis (PI. XX. fig. 10), still retains almost 

 this primitive type of skeleton, which in other species and varieties becomes very 

 variously modified. In Cladorhiza ji^nnatula, Schmidt," the pinnse are borne only on 

 two opposite sides. In the typical Cladorhiza ahyssicola, Sars, the main axis becomes 

 branched ; this may take place both above and below, giving rise to branches in the 

 one case and to anchoring rootlets in the other. The pinnae may be confined to a certain 

 part of the stem only, where they attain a great development. A good example of 



1 Jahresh. Comm. JFiss. Untersuch. d. deutsch. Mecre, &c. 



2 Jahresh. Comm. iViss. Untersuch. d. deutsch. Meere, Jahrg. i., ii. p. 119, pi. i. figs. 14-16. 



