Anatomy of the Kingfishers. 121 



on the vinculum, whereas digits 2, 3, and 4 could be flexed 

 independently of the hallux by contraction of the communis 

 muscle. In the Kingfishers, where the hallux is supplied by 

 the communis, a similar functional result is brought about 

 in another way. The hallux cannot be flexed independently 

 of the other digits by the action of the communis, as the 

 vinculum from that runs down to the hallucis tendon ; but 

 digits 3 and 4 may be flexed, independently of the action of 

 the hallux, by the hallucis muscle. 



In this communication I do not propose to enter into the 

 osteological modifications displayed in these Kingfishers, but 

 I may mention that they also provide valuable evidence as 

 to the relative specializations of eutaxic and diastataxic 

 forms. I may now sum up in a few words. When the 

 anatomy of Kingfishers is examined, it is found that the 

 differences present may, in a number of cases, be regarded as 

 showing a greater or less degree of specialization. The 

 group is to be regarded as marching in a definite direction, 

 many of the organs tending towards definite changes which 

 may be summed up as specialization. There is no rigid 

 correlation between the degrees of specialization of different 

 organs in the same species ; in some species certain changes 

 shoot out beyond others, but there is a general correlation, 

 so that if any species be far advanced in one organ it is 

 more likely to be far advanced in other organs, or to have a 

 higher average of advance among all its organs, it being 

 remembered that advance in such anatomical arguments 

 means change from common, ancestral, or generalized type, 

 whether such change be evolution or involution. The 

 change from diastataxy to eutaxy is one of these advances or 

 specializations, and in the Kingfishers, as in the Columbidai, 

 it is associated with a high average of advances in other 

 organs. I am not here concerned with what may be called 

 the motive force of specialization. It is plain that the 

 mode of its occurrence offers a specious argument to 

 those who would see in evolution evidence of a directive 

 impulse, resident in organisms, and the active agent in their 



