438 THE AQUARIAN NATURALIST. 



too refined for detection by human sense ; like the 

 gentleman who was always 



" Washing his hands with invisible soap, 

 In imperceptible water." 



The movements are of two kinds ; the whole avi- 

 cularium sometimes bending to and fro, so that the 

 head occasionally reclines as far back in proportion 

 as when a bird lays its head between its shoulders. 

 The other movement is merely the opening and closing 

 of the lower mandible, which gapes widely, and con- 

 tinues thus expanded, but stationary, when the whole 

 Zoophyte has perished. 



These movements are frequently so lively, that, 

 notwithstanding the excessive minuteness of the 

 Avicularia, the agitation of several at once proves very 

 inconvenient for microscopical observation. Though 

 numerous on a specimen, not more than one indi- 

 vidual is ever met with on any single cell. The 

 avicularium is itself semitransparent; yet, further 

 than has been described, no subordinate parts have 

 been detected. 



Here, then, is a fine subject for investigation by 

 the sea-side inquirer : Are these Avicularia parasites 

 that live fixed immoveably to a certain spot ? Are 

 they an integral part of the Zoophyte ? What rela- 

 tion do they bear to the cell, or to the polyp on 

 which they reside ? Many observers have been in- 

 duced to conclude them to be of a parasitical nature ; 

 nevertheless, they are evidently integral parts of the 

 Zoophyte, in so far as they are constantly formed along 

 with new or reproducing portions ; and it would seem 



