MEN IP E A FUGUEBIS. 363 



being called Hippocrepia, or Horseshoe animals, because the tentacles are arranged in a shape 

 resembling that of a horseshoe, it will be, perhaps, hardly necessary to apologize for the 

 introduction of so many technical terms, the fact being that the minute dimensions of the 

 objects have caused them to escape popular observation, and to depend for their nomenclature 

 upon the learned and scientific. Still, the technical phraseology is never employed where its 

 use can be avoided, and when circumstances render its introduction inevitable, its meaning 

 and the reasons for its employment are always given. 



We now arrive at another family, the Cellularidae, where the general shape resembles that 

 of the preceding family, but the cells, instead of being arranged round an imaginary axis, and 

 st) forming cylindrical branches, are arranged on the same plane. A magnified example of 

 tins family is the Cellular ia peachii, so called in honor of the eminent naturalist, Mr. Peach. 



In a creature belonging to the genus Menipea, found in Tierra del Fuego, and termed from 

 its habitat, Menipea fugueris, the curious "operculum" closes or rather guards the mouth 

 of the cell. In this genus it is in the form of a simple spike. This species is found at low 

 water. 



The avicularium is an object which is set somewhere about the middle of a cell, and 

 always upon its outside, and assumes various shapes in the different species of polyzoa. 

 What may be the precise nature of the avicularia is at present rather a mystery, and no one 

 can definitely pronounce them to be actual portions of the cell, or merely parasites that remain 

 affixed to the same spot. In all cases there is a decided resemblance to the head of a bird, 

 though in some species the similitude is closer than in others. Only one avicularium is to be 

 found on a single cell, though many cells do not possess these strange appendages. 



By close examination, it will be seen that the avicularium can be roughly distinguished 

 into three portions : namely, a base by means of which it is attached to the cell, a rather large 

 head, and a movable spine like the lower mandible of a bird's beak. In those examples where 

 the avicularium is seated directly upon the cell, the only movement is that of the lower 

 mandible, which opens and shuts with a continual motion, as if it were a veritable head of a 

 hungry bird snapping at its food. In those cases, however, where the base is lengthened into 

 a neck, the entire head is endowed with motion, nodding up and down in the most lively 

 manner, very like those wooden birds sold in the toy-shops, whose head and tail are alternately 

 raised and depressed by means of strings and a weight. But whether the head moves, oris 

 still, the jaws continually open and shut, and will often inclose between their parts any small 

 worm that may happen to come across their path, and have even been known to seize each 

 other in their grasp. 



When the beak has seized a victim, and the mandibles closed upon it, they retain their 

 grasp with astonishing tenacity, and when, as sometimes ha|>pens, two avicularia have seized 

 the same worm, the unfortunate victim is rendered entirely helpless by the grasp of its foes. 



The purpose of these objects seems to be rather dubious, but two conjectures have been 

 offered, which at all events are worthy of notice. 



According to the opinions of some observers, the avicularia answer the purpose of police, 

 and force intruders to leave the spot where their presence might do harm to the creature on 

 which they are placed. This duty seems, however, to be performed by the vibracula, and we 

 must search for another theory for the true object of the avicularia. Mr. Gosse has put 

 forward a conjecture which is not only highly ingenious, but bears with it the elements of 

 probability. 



" More than one observer," he remarks, "has noticed the seizure of small roving animals 

 by these pincer-like beaks, and hence the conclusion is pretty general, that they are in some 

 way connected with the procuring of food. But it seems to have been forgotten, not only that 

 these organs have no power of passing the prey thus seized to the mouth, but also that this 

 latter is situated at the bottom of a funnel of ciliated tentacles, and is calculated to receive 

 only such minute prey as is drawn within the ciliary vortex. I have ventured to suggest a 

 new explanation. 



" The seizure of a passing animal, and the holding it in a tenacious grasp until it dies, may 

 be a means of attracting the proper prey to the vicinity of the mouth. The presence of 



