APPENDIX 423 



other animals organs become externally separated from the 

 body, so that locomotive organs, digestive organs, sexual 

 organs, remain connected with the body only by a peduncle. 



This occurs in Zoophytes, for instance in the Siphonophora, 

 in lower forms of animals generally. It also liappens that 

 organs of this kind separate from the whole and swim about 

 independently; that sexual organs, for example, leave the 

 common body, and, provided with visual and auditory organs, 

 move freely in the water ; and that from the mingling of the 

 sexual elements of these isolated sexual organs new animals 

 arise. It even happens that in the course of evolution such 

 sexual organs come to be the principal form of the species, 

 while the original stock gradually dwindles away — ^just as 

 (and the comparison might be pursued far) if the separate 

 blossoms of a tree, male and female, separated and moved 

 about freely, and gradually in the course of evolution came to 

 exist as independent species, while the original tree gradually, 

 as such, disappeared. 



The Medusas afford instances of both these kinds of 

 phenomena. 



Again I will illustrate the subject by a brief reference to 

 another class of facts, namely, those of the social life of some 

 animals. In a bee-hive there are, as is familiarly known, 

 different kinds of individuals: there are the queen, the 

 drones, and the workers. In a community of animals allied 

 to these, the ants, and also in Termites, we have still another 

 class of specialised members, called, because they serve for 

 the protection of the social body, soldiers. These ditlerent 

 classes all work together for the goodof the whole community 

 in the wonderful manner known to all of us. 



How can we account to ourselves for the origin of these 

 different forms ? Only by this explanation : that they have 

 all been derived from a single primitive form, the organs of 



