58 THE VOrAGE OF H.M.S. CHALLENGER. 



bodies enclosed, differs obviously both in colour and consistence from the proper 

 parenchyma, and can be easily drawn off. This peculiarity is of course of very doubtful 

 importance. I have very often had occasion to speak of the low systematic significance 

 of similar properties of the skin, and it is sufficient to peruse the lines which F. E. 

 Schulze devotes to the matter in his paper on Hircinia ^ in order to become convinced 

 that species based on such characters are very doubtful. The more the dermal membrane 

 is charged with foreign bodies the more easily can it be drawn off, and on the other hand 

 it is obvious that the number of foreign bodies enclosed in the membrane depends on the 

 nature of the surrounding ground. 



Of course it cannot be denied that the tendency to form such a cortex of foreign 

 bodies may become hereditary, but stUl its systematic application appears to me to be 

 rather dangerous ; and with respect to my Cacospongia 'riiurrayi, it is the less necessary 

 as the sponge shows another peculiarity of an undoubtedly more constant character, 

 concerning the structure of the skeleton. In Cacospongia murrayi the skeleton is, 

 so to speak, composed of two skeletons. There are vertical primary fibres 0'15 mm. 

 in diameter, and rather finer secondary fibres united to the first-mentioned in a more 

 or less regular horizontal direction, and this system of primary and secondary fibres 

 is enveloped in an irregular network of still finer fibres (0'015 mm. in diameter on an 

 average), originating both from primary and secondary ones, but forming far smaller 

 meshes. PL VI. fig. 8, representing the outer surface of a portion of skeleton, when 

 seen against the light, illustrates this peculiarity sufficiently well. The outermost points 

 of the primary fibres are either pretty well developed, and accordingly project from the 

 outer surface into the substance of the cortex, without giving rise, however, to any 

 unevenness on its outer surface, or are very short, and represented only by low thickenings 

 over the intersecting poiat of the primary and the uppermost secondary fibres. The 

 histological character of the cortex presents no deviations from the usual connective 

 tissue of Keratosa, except that the cellular elements, stellate and fusiform cells, ai-e very 

 scanty ; the histological and anatomical structure of the proper parenchyma is that of 

 typical Spongidse. 



The species is named in honour of Mr. John Murray of the Challenger Expedition. 



Colour. — Outer surface grey, parenchyma pale greyish, skeletal fibres brownish. 



Habitat. — Station 163b, June^S, 1874, off Port Jackson; depth 35 fathoms, hard 

 ground. 



Cacospongia vesiculifera, n. sp. (PI. IV. fig. 2 ; PL VI. fig. 9). 



This form, like the one just described, isr epresented in the Challenger Collection 

 by a single specimen, and is in its turn provided with a sj^ecial cortex, but here its 



1 Zeitschr. f. toiss. Zool., Bd. xxxiii. p. 14, 1880. 



