38 THE VOYAGE OF II. M.S. CHALLENGER. 



As I remarked before, the peduncle is solid, the endodermic cavities of the adjacent 

 tubes not extending deeper than its superior part. Its cellular elements consist of amoeboid 

 cells, distinguished by very large granules (PI. III. fig. 3) ; there are also amongst them 

 common amoeboid cells, such, for instance, as F. E. Schulze 1 describes in Sycandra 

 ra/phanus. The same elements are also to be found in the mesoderm of the tubes, but 

 much more sparsely than in the peduncle. The outer epithelium of the tubes proved also 

 to be coarse-grained ; that of the peduncle could not be discerned. I regard these 

 coarse-grained mesodermic cells as carrying nutritious elements, and explain their 

 predominence in the peduncle by its solidity. 



The larger Challenger specimen is represented in PI. I. fig. 2. 



To the habitat of Leucosolenia blanca, as given by Hseckel (loc. cit., p. 39), must be 

 added the Mediterranean Sea. The Sponge has been found in the Gulf of Naples 

 (Vosmaer 2 ), and there are also at the Institute in Graz some specimens from the Adriatic. 



Colour. — Pale yellowish. 



Habitat.— Station 75, July 2, 1873; lat. 38° 37' N., long. 28° 30' W.; off the 

 Azores; depth, 450 fathoms; sand. 



Leucosolenia challengeri, n. sp. (PI. I. fig. 1 ; PI. III. fig. 4). 



This form can be distinguished from other species of Ascetta, in the sense of Hseckel, 

 by the presence of a special set of triradiate spicules covering the outer surface of 

 the colony, these spicules being all sagittal, while the triradiate spicules of the interior 

 are all regular. The only specimen I find in the Challenger collection presents the 

 soleniscus-form, the diameter of the tubes, i.e., individuals of the colony, varying from 

 - 3 to 0'8 mm. ; the pseudopores are still narrower, rarely exceeding 0"28 mm. in diameter; 

 the oscula, sparsely scattered here and there, possess the same dimensions, or are rather 

 larger. The whole forms an irregularly oval body 30 mm. long and 20 mm. broad in its 

 thickest part, presenting a compact web of minute tubes and terminating in a short 

 (2 mm.) peduncle. This latter is solid, at least in its interior part, and so far as the state 

 of preservation permits one to judge, contains cellular elements like those in the peduncle 

 of Leucosolenia blanca. 



Skeleton. — Two forms of spicules are to be distinguished, — regular and sagittal 

 triradiate. 



The regular spicules are very like those of Leucosolenia coriacea, John., var. multicavata, H. 

 (Kalkschwamme, Bd. ii. p. 25) ; their rays (018 mm. long) are slender (16 to 20 times 



1 Ueb. d. Bau. u. Entw. v. Sycandra raplianus, Zeitschr.f. vriss., Zool, Bd. xxv., Suppl. p. 253, 1875. 



5 Voorloopig berigt omtrent h. onderzoek aande Nederl. werktafel in li. Zool. St. te Napels, Haag, 1881, p. 5. 



