THE SPECIES 



251 



from the stock of their common properties, as we might read 

 them off a measuring-rod ; but by this means we learn 

 absolutely nothing about the methods Nature has employed 

 in creating relationships. 



THE COLONY 



Hitherto we have considered only such organisms as came 

 from an egg, and by means of eggs gave rise to independent 

 offspring. There are also, however, organisms that do not 

 arise from independent eggs, but from germs that remain 

 connected with the mother organism. We call such germs 

 " buds," and the organism arising from a number of buds is 

 no longer an individual, but a colony composed of persons. 

 The most striking instances of this kind are given by certain 

 siphonophores. These multiform colonial medusae are com- 

 posed of a series of individual persons, each of which has its 

 own organs for food-capture, for feeding and for sexual pur- 

 poses ; but all the persons are connected together by a 

 common alimentary canal. 



Colonies composed of a number of similar persons give 

 the impression of being a unified animal, possessing, however, 

 many mouths, many arms, and so forth. The function- 

 circles resemble those of an individual animal in all particulars. 

 They have arisen through a definite rule, and have a definite 

 rule of function. Accordingly, thgre is no reason why animal iX 

 colonies should not be called subjects. 



ANIMAL COMMUNITIES 



Animal colonies such as we have described are distin- 

 guished by the fact that the individual persons together form 

 a fixed framework. It is easy to imagine that there are other 

 colonies in which the individual persons are not connected in 



