TRANS LA TOR 'S PRE FA CE xvil 



in explanation of the origin of adaptations than the case of 

 the woodpecker. This bird lives entirely on insects, and 

 only catches insects in one way — a A^ery peculiar way. It 

 probes the holes in the bark of trees made by insects, or 

 makes holes itself, and then inserts its long pointed tongue, 

 whose tip is provided with recurved papillse, like a narrow 

 bottle -brush, and with this extracts the ma^'^ots. The 

 rapid protrusion of the tongue to a considerable distance, 

 and its sudden retraction, are rendered possible by the 

 elongation of the processes of the hyoid bone to which the 

 tongue is attached. These processes are bent upwards and 

 forwards over the back of the skull and inserted near the 

 orbits. iSTow, in all birds the tongue is attached to the 

 hyoid bone and moved by the muscles connected with that 

 bone : in nearly all birds the tongue is muscular and mobile. 

 It is admitted even by Weismann's adherents that the size 

 and shape of bones, the size and shape of muscles, are in 

 the individual modified by the use which is made of them 

 It will also probably be admitted that the modification is 

 such as to facilitate the operations in which they are used. 

 Therefore in every generation of woodpeckers — which birds, 

 in the struggle for existence, had to be content to pick up 

 a living on tree-trunks or starve — the constant use of the 

 tongue in extracting insects from holes in trees must have 

 elongated the tongue and hyoid bone, and increased the 

 power of protrusion of the organ in each individual. The 

 Keo-Lamarckians believe that these individual modifications 

 were inherited in some degree, so that a greater modification 

 in the same direction was produced in the offspring, and in 

 this w^ay it is easy to understand how the degree of special- 

 isation we now see was produced. 



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