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CHAPTERS ON EVOLUTION. 



the two sexes are developed in nearly equal numbers. It may be 

 conceded that in the case of the bees, as insects of specialised type, 

 we are dealing with insects in which true unfertilised eggs develop 

 simply into drone or neuter-insects. But in the lower plant-lice, 

 the process is more nearly related to the budding of the zoophyte. 

 Each aphis, produced viviparously from the parent-body, grows from 



FIG. 197. COMPARISON OF DEVELOPMENT in (i) a Flowering Plant ; (2) a Zoophyte ; and (3) 

 a Colony of Plant-Lice (Aphides). 



a structure which, whilst it resembles a true egg, does not pass 

 through the development of that body, and is therefore called a 

 pseud-ovum. Gradually this " pseud-ovum " grows into the likeness 

 of the aphis, which, after birth, will develop within itself like 

 bodies, and thus carry on the work of continuing the species in time. 

 If we suppose that the aphides remained connected together (Fig. 

 197, 3), instead of preserving a distinct structural identity, we should 

 reproduce in this insect-tribe an exact facsimile of the zoophyte- 



