74 THE AMERICAN MONTHLY [March 



very keen. We know of instances in almost every group 

 of animals, where some dominating instinct will keep 

 animals together in thousands and even millions, although 

 separately they would have much more chance of ob- 

 taining their proper food supply. I need only remind 

 you for a moment of the flights of locusts, the shoals of 

 herrings and mackerels, and the armies of lemmings 

 travelling enormous distances in search of food. 



Again, in others the instinct of preservation of the spe- 

 cies seems to be stronger than the instinct of self-preser- 

 vation, and we find communities organized, chiefly among 

 the insects; here the life of the individual is sunk in 

 favor of the life of the community, and, as in the case 

 of the bees, the workers will toil and die in the service 

 of their queen. But indeed in all gregarious animals the 

 instinct of mutual aid is often developed out of the 

 instinct of self-preservation, for they have learnt that 

 united they stand while divided they fall, and so danger 

 is often averted by a combined assault on the enemy. 



Such instincts, however, we cannot look for in the un- 

 reasoning vegetable kingdom, or even in the lower clas- 

 ses of the animals in which no central nervous system 

 has as yet been evolved, and still some most remarkable 

 instances of collective life are found in some of these 

 groups. What for instance are we to think of the ap- 

 parent unity of impulse and life of such a compound 

 Ascidian as Pyrosoma, or of a polyzoou like Cristatella, 

 and finally how are we to look upon a compound hydro- 

 zoon like Physophora, in which each individual or person 

 has a difi'erent function assigned to it? Must we look 

 upon these as single individuals, or as a number associa- 

 ted together as it were in partnership, sharing the profits 

 made by the whole number? 



Partnerships they may be called, but the partnerships 

 which I "wish to speak about are of a diff'erent nature, for 



