IIAIIDWICKE'S SCIENCE-GOSSIP. 



Fig. 24. — Cyliiidro-cruciform ; shafts densely spi- 

 culate. 



Tig. 25— Spined, cylindrical, x 200 : 22, 23, 21, 

 and 25 are found in abundance in the coriaceous 

 sbeath (Polythoa), less plentifully in the inter- 

 stices of fibrous axis, and very rare in the body of 

 the sponge. 



Fig. 26.— Multi-hamate, bi-rotulate ; shaft cylin- 

 drical, slight, papillate ; x GO. 



Fig. 22. 



showing stellate 



rig. 27.— Side view of ditto, 

 arrangement of the hooks. 



Fig. 28. — Abnormal form of the above, x 100. 



Fig. 29. — Spiculated cruciform spiculum, as- 

 sociated with the above in the body of the sponge, 

 and the interstices of the fibrous axis ; x 200. 



Fig. 23. 



Fig. 30. — Simple, bi-hamate, acerate, having each 

 end of the spiculum curved in the form of a hook ; 

 X 400 ; very rare. 



Fig. 31. — Quadri-hamate ; common in the body of 

 the sponge ; x 1,000. 



The above do not comprise all the forms of 

 spicula to be found in this remarkable sponge. 

 Professor Thomson has taken a great number of 



specimens, and his promised memoir on this genus 

 is anxiously looked for. 



Fig. 1i. 



Since writing the above, I have had the oppor- 

 tunity of examining a series of specimens belonging 

 to the Rev. J. Crompton, of Norwich. Three of them 

 were of considerable interest, as throwing light 



U-' 



Fig. 25. 



Fig. 26. 



upon the parasitic nature of the Polythoa. One of 

 the specimens was almost entirely divested of the 

 parasite, but near the top was a small piece of some 



frondose alga, attached, or rather entangled, round 

 the Glass-rope by several tendril-like filaments. 



