234 



LIFE, IN ITS INTERMEDIATE FORMS. 



them t Why do some specimens possess them and not 

 others? Why are some species of a genus furnished with 

 them while some are destitute of any such appendages, 

 though essentially the same in every other respect ? No 

 light is thrown on these questions by anatomical exami- 

 nation. It would appear that the animal within is quite 

 independent, organically, of the " bird's head," for, as Dr 

 Eeid has remarked, and as we have personally observed in 

 several species, the " bird's head " continues to move for 

 a considerable time after the death and decomposition of 

 the polype. It has been suggested that the use of the 

 organ is to grasp and kill passing animalcules, which then 

 may be drawn into the cell by means of the ciliary cur- 

 rents of the tentacles ; and this appears not improbable, 

 and receives confirmation frcm the toothed structure of 

 the beak. 



The organ in question, with its singular function, may 

 minister to the support of the common life in another way 

 less direct but not less effective. The seizure of a passing- 

 animal, and the holding of it in the tenacious grasp until 

 it dies, may be a means of attracting the proper prey 

 to the vicinity of the mouth. The presence of decom- 

 posing animal substance in water invariably attracts crowds 

 of infusory animalcules, which then breed with amazing 

 rapidity, so as to form a cloud of living atoms around 

 the decaying body, quite visible in the aggregate to the 

 unassisted eye, and these remain in the vicinity, playing 

 round and round until the organic matter is quite con- 

 sumed. Now, a tiny Annelid or other animal, caught by 

 the bird's head of a Polyzoan and tightly held, would 

 presently die ; and though in its own substance it might 



