82 EX VIRIBUS VIVIMUS. 



unaccountably called vegetative repetition — for it is 

 quite as truly animal or animative repetition — is an 

 arrested production of zooids by budding ; that it 

 is, in fact, a merging of many individualities in one. 

 This, we see, in many cases, like being compared 

 with like, is accompanied by increased longevity. The 

 Taenia which exhibits this tertiary aggregation in a 

 loose sort of way continues to develope from the 

 attached head, and to protract its individual duration 

 of life long after sexual organs have ripened and 

 death followed in the separated proglottides. In the 

 closely-allied Trematodes (flukes), in which the indivi- 

 duality is that of a secondary aggregate, death follows 

 reproduction ; as also in the Nematodes, which live 

 in similar conditions, and are structurally allied to the 

 other parasitic worms. In vegetals we find the same 

 relation holding good, the multiaxial plants being 

 the long-lived, the uniaxial the short-lived. That 

 tertiary aggregation only has this accompaniment as 

 long as it implies an increased comparative evolution, 

 is seen in the fact that the Mollusca and Vertebrata, 

 supposed to be secondary^ aggregates, are longer 

 lived than many tertiary aggregates ; whilst similarly 

 the relation of expenditure to longevity considerably 

 qualifies the influence of tertiary aggregation. The 

 Annelids of high tertiary aggregation, i. e. of many 

 segments (e.g. Lumbricus and marine forms), are 



That is aggregates compounded of primary aggregates; primary 

 aggregates being simply cells. 



