132 STUDIES IN ANIMAL LIFE. 



of the food. But your eye detects a noticeable dif- 

 ference between this polype in its capsule, and the 

 six semi-transparent masses in the second capsule ; 

 although the two capsules are obviously identical, 

 they are not the same ; a differentiation has taken 

 place. Perhaps you think that six polypes are 

 here crowding into one capsule ? Error ! If you 

 watch with patience, or if you are impatient yet 

 tolerably dexterous, you may press these six mass- 

 es out, and then will observe them swim away, so 

 many tiny jellyfish. Not polypes at all, but jelly- 

 fish, are in this capsule ; and these, in due time, 

 will produce polypes, like that one now waving 

 its tentacles. 



Having made this observation, it will naturally 

 occur to you that the polype stem which bore such 

 different capsules as are represented by these two 

 may perhaps be called a colony, but it is a colony 

 of different individuals. While they have all one 

 skeleton in common, nutrition in common, and res- 

 piration in common, they have at least one differ- 

 entiation, or setting apart for a particular purpose, 

 and that is the reproductive capsule. This is an 

 individual as much as any of the others, but it is an 

 individual that does nothing for the general good ; 

 it takes upon itself the care of the race, and be- 

 comes an " organ" for the community ; the others 

 feed it, and it is absolved from the labor of nutri- 

 tion as much as the arm or the brain of a man are. 



From this case, let us pass to the group of jelly- 



