SEGMENTAL INDIVIDUALS 113 



obliged to abolish colonial structure in order to obtain higher 

 complexity of function. 



For the Continuously Megazooidal is the highest form 

 of living Continuity which is truly colonial in nature, or 

 in which distinct multicellular organisms leading practically 

 independent existences remain attached to each other to 

 make the Individual. But as the lateral fusion of zooids 

 in the megazooid is not so complete as to leave no indica- 

 tions of what has happened, so the serial fusion of megazooids 

 in the Segmental organism has not banished all traces of 

 megazooidal derivation ; and it is to such areas as by their 

 traces of megazooidal boundaries indicate megazooidal 

 derivation that the term " segments " is here applied, the 

 organisms composed of these being called " Segmental " 

 organisms. 



But a Segmental organism is not necessarily a Segmental 

 Individual, for the latter presents itself in two main classes ; 

 in one being composed of many separate segmental organisms, 

 and in the other of one organism. And it is to be noted that 

 in the former the separate organisms are not segments, 

 but are composed of segments just as in the latter. 



The two main types of Segmental Individual are there- 

 fore The Discontinuous Segmental and the Continuous 

 Segmental. 



The Discontinuous Segmental Individual we shall do no 

 more than mention, intensely interesting as it is. There 

 can be little doubt that it originated as a branching off from 

 the main road of Evolution, and that it was not the ancestor 

 of the Continuous Segmental Individuals from which man 

 was ultimately derived. Typical present-day representatives 

 of the class ere the Aphis and Honey-bee Individuals, well 

 known as striking examples of Alternation of generations 

 and Parthenogenesis. 



THE CONTINUOUS SEGMENTAL INDIVIDUAL. 



The number and variety of Continuous Segmental 

 Individuals in Nature are immense, including among others 

 such diverse forms as Echinoderms (probably), Annelids, 

 Molluscs, Ascidians, Fishes, Birds, Reptiles, and Mammals ; 



8 



