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



Genus 2. PohjJophus, n. gen. 



1872. Gray, Ann. ami Mag. Nat. Hist., ser. 4, vol. x. p. 137. 



1873. Gray, Op. cit., ser. 4, vol. xi. p. 234. 

 1873. Carter, Op. cit., ser. 4, vol. xii. p. 361. 

 1875. Carler, Op. cit, ser. 4, vol. xv. p. 118. 



1877. Marshall and Meyer, Mittheil. Zool. Mus. Dresden, vol. ii. p. 261. 



History. — Among the Hexactinellida which Dr. A. B. Meyer brought with him from 

 Zebu (Philippines), Gray found in 1872 a comparatively large specimen which bore 

 peculiarly disposed projecting tufts of needles on the posterior half, while the anterior 

 extremity exhibited the wide aperture of a spacious gastral cavity. He compared this 

 sponge with Tetilla 'polyura, 0. Schmidt, while Carter, to whom it was handed over, at 

 once detected a close relationship between this form and his Rossella antarctica. Gray 

 therefore named it Rossella philippinensis. In 1873 Gray received some young buds of 

 the same sponge, which were also obtained from Dr. A. B. Meyer. These were briefly 

 described under the title Psetalia glohidosa, Gray. In 1875, however, Carter published 

 a detailed description with good figures of the form and structure both of the older 

 specimen and the young buds [Psetalia glohidosa, Gray). Both the general structure 

 and the form of the spicules exhibited the close resemblance which those specimens bore 

 to Carter's Rossella antarctica. Finally, Marshall and Meyer subjected these results to a 

 close scrutiny in 1877, and described in detail the form and structure both of the entire 

 sponge and of the various spicules. 



The characteristic anchors found in the root and tuft-spicules were regarded 

 by Marshall and Meyer not as homologous, but as analogous to the anchors in the 

 tuft-spicules of Euplectella, Semperella, and Hyalonema, since the double cross was 

 not found in these latter genera in the anchor head itself but further up in the shaft, so 

 that the anchor teeth could not be looked upon as modified rays of hexradiate spicules. 

 The nine distinct forms of spicules observed were found by Marshall and Meyer to be 

 distributed as follows : — 



A Appendicular spicules :— I C. Spicules of the parietes : — 



1. Eoot-spicules of anclior-like fomi. 5. Gastral and facial tive-rayeJ spicules. 



2. Uniaxial spicules of the spicular wreath. I 6. Six-rayed spicules. 



7. Uniaxial spicules. 



8. Rosettes. 



B. Spicules of the dermal skeleton : — 



3. Five-rayed spicules. 



4. Four-rayed spicules with tubercles. D. Gastral spicules : — 



9. Small six-rayed spicules. 



A young specimen, 5 mm. in diameter, in which the anchor-tufts were tolerably 

 well developed, already showed the same spicular forms in a similar arrangement. A 

 specimen preserved with its soft parts in spirit was found to be fiUed ■ftitli small green 

 and grey granules ; some cell -nuclei were seen, and here and there a fragment of 



