CROWS AND FLYING FOXES 25 



lent bulk of living matter. In the evening the 



crows begin to arrive in small numbers before 



the vanguard of the bats has started, increasing 



in their turn to large battalions until a period of 



maximum migration is reached, and then troops 



of bats are to be seen passing over still larger 



columns of crows in the opposite direction, the 



whole of the cross-migration occupying about 



half an hour. The reverse passage, namely, 



the matutinal flight, takes place towards sunrise, 



the bats returning from the mainland to rest 



for the day suspended in rows from the midribs 



of the palm leaves, the crows crossing over on 



their daily quest for garbage. This instance 



may be classed as one of convergent homing, 



the same trees affording hospitality in regular 



alternation to day-flying birds and night-flying 



mammals. 



Phanerozoa and cryptozoa are two well-marked 

 physiological groups, comprising between them 

 all the forms of animal life ; and the distinction 

 is paralleled by the following more fundamental 

 contrast between animals and plants. In general 

 habit and mechanism of growth the vegetable 

 kingdom as a whole exhibits positive phototaxis 

 in the wide sense, whereas the animal kingdom 

 as a whole seems to show negative phototaxis ; 

 the former proposition can be accepted without 

 question, but the latter requires substantiation. 

 Passing over the vast array of strictly cryptozoic 



