4 THE USES AND ORIGIN 



increases in complexity in ascending to more and more 

 highly organized types of animal life. 



***** 



In the present day it is commonly admitted that many 

 of the lowest forms of life cannot positively be assigned 

 either to the Vegetal or to the Animal Kingdom. Their 

 characters as living things are not sufficiently specific or 

 constant to enable us to say that they belong to one king- 

 dom rather than to the other. In some of their life-phases 

 such organisms seem to display the attributes of vegetal 

 life, whilst in others those of animal life are no less 

 pronounced. They constitute, in fact, an underlying 

 indeterminate plexus of changeable and more or less 

 related forms, appearing now as animals, now as plants 

 and they may give rise to descendants, or to a series of 

 them, totally unlike themselves and their own immediate 

 ancestors. Amongst such forms variability reigns supreme. 

 These creatures of circumstance, which become metamor- 

 phosed in a most striking and apparently irregular manner, 

 the writer has proposed* to include under the general 

 designation of ' ephemeromorphs.' True ' species,' in 

 the strict acceptation of the term, are not to be found 

 amongst them. 



Starting from this neutral and changeable ground, 

 however, forms of life appear that habitually reproduce 

 their like, either directly or indirectly ; some of which are 

 unmistakably members of the vegetal kingdom, whilst 

 others are no less characteristic representatives of the 

 animal world. 



Owing to the frequency and rapidity with which transi- 

 tions from vegetal to animal, or from animal to vegetal, 

 modes of growth have been observed to occur amongst 



* " Beginnings of Life," 1872, vol. ii. pp. 559, 571. 



