ZOOPHYTES. 389 



offence, like the motile spines and bird's head pro- 

 cesses of the Polyzoa, or the pedicellarise of the 

 Echinodermata I but it is difficult to assign a reason 

 for their peculiar situation. They vary much in num- 

 ber and size in different specimens of Hyd/r actinia, but 

 are rarely altogether absent." * 



The reflections of the able zoologist who first 

 called attention to these varied developments, and his 

 comparisons of them with those of another polype-form 

 which we have lately been observing, are so interesting 

 and instructive that you will not deein it needful that I 

 should apologize for citing them. " In our considera- 

 tion of the Hydractinia" he observes, " our attention 

 is arrested by the multitude of objects grouped together 

 to constitute a single animal, their variety in form, and 

 the sympathy which subsists between the different 

 parts. The . singular spinous skeleton ; the expanded 

 membrane of the polypary, with its beautiful internal 

 network of tubes and delicate peripheric prolongations ; 

 the alimentary polyps, some white and filiform, others 

 thick, fleshy, crimson, or yellow sacs, obligingly 

 everted, to expose their interior to our microscopic 

 eye ; the reproductive polyps, with their richly- 

 coloured generative sacs ; the sessile generative organs 

 of the polypary; the ophidian polyps, coiled in neat 

 spirals when at rest, but starting into furious action, 

 like a row of well-drilled soldiers, when injury is in- 

 flicted on the body to which they are attached ; and, 

 lastly, the tentacle polyps, floating in the water like 

 long and slender threads of gossamer, or dragging 

 up heavy loads of food for the common good ; — these, 

 together with the intimate relation and sympathy sub- 



* Dr. Wright, op. cit. 



