YOUNG BIRDS IN THE NURSERY 55 



ment and analysis, and any attempt to penetrate these 

 mysteries must take into consideration the far more 

 helpless condition displayed by the early post-embryonic 

 condition of such young in comparison with those of 

 more lowly types. This helplessness stands, apparently, 

 in direct relation to the increased vitality shown by the 

 adults. Yet it would not be true to say that the " cold- 

 blooded " types are more creatures of habit than the 

 warm-blooded ; nevertheless this difference of temperament 

 must be our starting-point in picking up the trail we 

 are all so anxious to find. 



In considering all organisms, or parts of organisms, 

 our standard of comparison is the distance they have 

 travelled from what must have been their starting-point : 

 in some cases this can be more or less accurately measured, 

 in others we must set up some hypothetical standard. 

 Where the departure from the type is slight we say that 

 the thing measured is " primitive," that is to say, it 

 represents, more or less nearly, the original, ancestral 

 condition ; where the departure is considerable, then, in 

 so far, it is " specialised." A dinghey is a more primitive 

 kind of boat than a racing skiff, which is a specialised 

 kind of craft, capable of performing, and designed for 

 performing, limited functions. But the term " primitive " 

 is a relative term. The old wooden three-decker battle- 

 ship is a " primitive " craft compared with the warship 

 of to-day, but compared with the ancient trireme it is 

 highly specialised. 



On the whole, it would be better, probably, if this 

 word " primitive " were used in a more restricted sense, 

 and were commonly replaced by the word " generaHsed." 

 But whichever word we elect to use, the idea, the mental 

 image we*desire to conjure up, is aj[state of things more 



