512 ANNUAL, BEPOKT SMITHSONIAN INSTITUTION, 1920. 



cellular organism. A comparison between these two kinds of associa- 

 tion suggests itself, and might be fruitful. 



To the fertilized egg from which comes the multicellular organism 

 corresponds the creative couple among the termites, and the female, 

 who contains the male in the form of spermatozoa filling her seminal 

 receptacle, among the social hymenoptera. Just as the fertilized egg 

 produces mortal somatocytes and virtually immortal gonocytes, so are 

 born in the insect societies neuters whose biological cycle is inter- 

 rupted and sexed individuals who are able to repopulate the associa- 

 tion. There is this difference : The fertilized egg is divided integrally 

 into blastomeres, leaving no residue, while the founders, or the 

 fertilized female founder, of the insect societies exist beside their 

 immediate descendants. But this difference is not fundamental, for 

 each offspring in a society of insects originates from a particle of the 

 hereditary substance of its parents, just as the cells of a multicellular 

 organism are only a fraction of the initial fertilized egg. 



The only important difference is this : The multicellular organism 

 is a concrete association in which the members are bound together 

 by anatomical connections, while the societies of insects are discrete 

 associations formed of anatomically independent elements, being un- 

 able to influence each other except through their ethological be- 

 havior. 



When we studied the origin of multicellular organisms, we recog- 

 nized that it was brought about by particularly favorable economic 

 conditions, not necessitating the emigration of the cells after their 

 division, and allowing them to exploit a territory in common ; to the 

 same cause may be attributed the origin of insect societies: The 

 termites as well as the hymenoptera are nest-building animals, and 

 the nest, abundantly provided with food, constitutes for these organ- 

 isms a privileged territory where the offspring may live in the midst 

 of the family. 



We have previously shown the contrast which exists between the 

 puny multicellular organisms, all of whose cells are equally repro- 

 ductive, without differentiation, and the powerful multicellular or- 

 ganisms with much more numerous cells, among which there is pro- 

 duced a differentiation into gonocytes and somatocytes, the latter 

 being the humble servants of the former and sooner or later passing 

 into a lifeless condition. 



Similarly we know of familylike associations of insects or of 

 spiders in which all the individuals are equal, in which there are no 

 neuters, and these associations are but little developed and ephemeral, 

 for the necessities of the struggle for existence force an emigration 

 of the individuals. It is only in the societies of termites and of 

 hymenoptera that simple families have been able to become per- 

 manent populations, thanks to the appearance of innumerable in- 



