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



fused together irregulaiij', thougli occasionally also crossing one another in a regular 

 manner, so that a network surrounding rectangular meshes becomes formed. It seems 

 nowhere to show actually free cross spicules, yet very frequently the cavities of the 

 amalgamated cross fibres remain independent of one another, so that often two or three 

 hollow spaces lying close to one another, yet not connected, are cemented together by a 

 common siliceous mass. In these siliceous tubes the uncommonly wide cavity of the 

 axial cord is remarkable. It is often so wide that its diameter exceeds the thickness 

 of the wall about six times. It is to be regretted that the single specimen is much 

 bleached and macerated, so that it is not possible to say whether the almost complete 

 absence of all free siliceous bodies should be looked upon as a peculiarity distinguishing 

 this genus. To judge from the structure of the tissue, this sponge probably belongs 

 to the same genus as Farrea occa, Bowerbank. Since, however, only fragments of the 

 latter are known, it is still possible that they belong to the Euplectella cucumer, Owen, 

 on whose roots they were found, so that provisionally Farrea occa and Eurete simpli- 

 cissima, Semper, may be regarded as distinct from one another. An accurate examination 

 of the tissue of Euplectella cucumer would throw light on this question. Detailed 

 descriptions will shortly be given in the Zeitschrift fiir wissenchaftliche Zoologie." 



The description here promised was given by W. Marshall in 1875.^ Marshall first 

 confirms the general descrijDtion of Semper, and calls attention to the occurrence of 

 transverse divisional walls close beneath the orifices of some tubes. These he designates 

 by the name of sieve-plates, and is inclined to regard them as indicating the regular limit 

 of every " individual" properly so called. Of free spicules Marshall, like Semper, found 

 but a mere trace, and he therefore concluded that even the living sponge had none. 

 This view has again been definitely expressed by Marshall ^ after re-examination of 

 Semper's original specimen. 



The sponge minutely described by Carter under the name of Eurete farreopsis ^ was, 

 like the majority of objects of this nature that have to be dealt with, much macerated, 

 yet in some remnants of the dried soft parts, a number of free siliceous spicules could 

 still be found. From Carter's minute description I make the following excerpt as being 

 of very great importance : — " General form bush-like, composed of many tube-branches 

 anastomosing clathrously. Branches short, thick, cylindrical, hollow, formed of a delicate, 

 thin, reticulated wall, thickening from the growing margin towards the base or oldest 

 part. Orifices of branches respectively circular at first, then expanded, afterwards 

 funnel-shaped, becoming elliptical and contracted in the centre, where by the union of 

 the approximated parts of the margin, two circular orifices are formed, which grow into 

 two short, round, tubular branches in opposite direction, to divide again after the same 



1 Zeitschr.f. vdss. Zool., Bd. xxv. p. 181. 



2 Mittheil. K. Zool. Mus. Dresden, ii. p. 272. 



^ Ann. and May. Nat. Hist, ser. 4, voL xix. p. 122, 1877. 



