OBJECTIONS TO THE THEORY 327 



adds, may likewise be found between the pedicellarise of 

 the star-fishes and the hooks of the Ophiurians, another 

 group of the Echinodermata; and again between the pedi- 

 cellarise of sea-urchins and the anchors of the Holothurise, 

 also belonging to the same great class. 



Certain compound animals, or zoophytes as they have 

 been termed, namely the Polyzoa, are provided with cu- 

 rious organs called avicularia. These differ much in 

 structure in the different species. In their most perfect 

 condition, they curiously resemble the head and beak 

 of a vulture in miniature, seated on a neck and capa- 

 ble of movement, as is likewise the lower jaw or man- 

 dible. In one species observed by me all the avicularia 

 on the same branch often moved simultaneously back- 

 ward and forward, with the lower jaw widely open, 

 through an angle of about 90°, in the course of five 

 seconds; and their movement caused the whole polyzoary 

 to tremble. When the jaws are touched with a needle 

 they seize it so firmly that the branch can thus be 

 shaken. 



Mr. Mivart adduces this case, chiefly on account of 

 I the supposed difficulty of organs, namely the avicularia 

 of the Polyzoa and the pedicellarisB of the Echinoder- 

 mata, which he considers as "essentially similar," having 

 Ibeen developed through natural selection in widely dis- 

 inct divisions of the animal kingdom. But, as far as 

 structure is concerned, I can see no similarity between 

 tridactyle pedicellarise and avicularia. The latter resem- 

 )le somewhat more closely the chelae or pincers of Crus- 

 fiaceans; and Mr. Mivart might have adduced with equal 

 ippropriateness this resemblance as a special difiiculty; or 



