STUDIES IN ANIMAL LIFE. 133 



fish, called Siphonophora (siphon-bearers) by natu- 

 ralists, and we shall see this union of very differ- 

 ent individualities into one inseparable colony still 

 more strikingly exhibited : there are distinct indi- 

 viduals to feed the colony, individuals to float it 

 through the water, individuals to act as feelers, and 

 to keep certain parts distended with fluid, and final- 

 ly reproductive individuals. All these are identical 

 in origin, and differ only by slight differentiations.* 

 Here we have obviously an approach to the more 

 complex organism in which various distinct organs 

 perform the several functions, only no one calls the 

 organism a colony. 



The individuals composing one of these Siphono- 

 phora are so manifestly analogous to organs, that 

 their individuality may perhaps be disputed, the 

 more so as they do not live separately. But the 

 gradations of separation are very fine. You would 

 never hesitate to call a bee or an ant an individual, 

 yet no bee or ant could exist if separated from its 

 colony. So great is the " physiological division of 

 labor" which has taken place among these insects, 

 that one can not get food, another can not feed it- 

 self, but it will fight for the community ; another 

 can not work, but it will breed for the community ; 

 another can not breed, but it will work. Each of 



* Compare LEUCKART : Ueber den Polymorpliismus der Individ- 

 ven. GEGENBAUR : Grundzuge der Vergleichende Anatomie ; and 

 HUXLEY'S splendid monograph on the Oceanic Hydrozoa, published 

 by the Ray Society. 



