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 



