from the North Sea. 89 



innermost layers, by being bent, show that it existed when 

 the needle was smaller. This may also possibly be an 

 indication that the specimens of Hyalonema examined are old 

 individuals. 



The long needles of Hyalonema present a singularity first 

 observed by Dr. Gray, and of which no trace is seen in our 

 sponge. Their free ends have hooks placed in rings or spirals 

 directed towards the thickest point of the needle. Professor 

 Schultze expressly remarks that this cannot depend on the 

 exterior layers having been partly broken. It is an uncom- 

 mon case. 



Professor Schultze, who described the oscula of the flattened 

 surface of the head of his great Hyalonema^ found this same 

 surface in the smaller younger specimens covered by a net- 

 work of spicules similar to that which covers the free end of 

 Euplectella cucumer^ Owen, and E. aspergillum^ Owen*. No- 

 thing similar is to be found in our sponge. 



The head of the large specimen of Hyalonema examined 

 by Professor Schultze shows a great number of circular holes, 

 with a diameter of nearly a line, surrounded by bundles of fine 

 siliceous needles, radiating in all directions from their edges. 

 They are not at all to be found in our sponge. Professor 

 Schultze regards them as ''chimneys" (that is, oscula); but 

 these are situated, as shown above, in Hyalonema as in our 

 and many other species, on the free surface of the head. Pores 

 for entering currents they cannot be. In their present form 

 they are probably foreign to the structure of the sponge, tubes 

 formed by the same parasitic zoophyte which Prof. Schultze 

 discovered in their yellowish-brown clothing, and the urti- 

 cating organs and arms of which he recognized. 



In looking back on what is said above — the differences 

 (which may depend partly on distinction of species or different 

 ages, partly on incomplete observation), the affinities in the 

 most important points (in the form of the head, with its great 

 oscula on the free surface, the spicules in its interior radiating 

 around the upper end of a stem composed of spindle-shaped 

 siliceous needles) — it seems to follow that the little sponge 

 which I have described, from the great depth of the North 

 Sea, is a Hyalonema in its complete state, with its stem un- 

 injured, and with its roots. But with regard to certain dif- 

 ferences — the absence of amphidisci (which seem to belong to 

 the propagation), the much shorter spindle-shaped needles and 

 their little-developed secondary forms — it seems probable that 

 the specimens I have described are young individuals of a 



* Loc. cit. p. 9; Owen, Trans. Zool. Soc. iii. p. 203, pi. 13 j Trans. Linn. 

 Soc. xxii. pi. 21, see footnote, p. 118. 



