108 Mr Macgillivray's Remarks on the Middle Clarv, 



increase so as seriously to add to its disease, or vermin may 

 become a disease, and injure or destroy the animal ; but these 

 are conjectures rather than facts. It is a fact, that birds 

 liable to be infested by vermin are quite unable to rid them- 

 selves of their tormentors, the latter enjoying almost perfect im- 

 munity, especially about the head, which, with others, is a rea- 

 son why the head, and especially the anterior part of it, should 

 be more densely peopled than the other parts of the body. It 

 is asserted that gallinaceous and passerine birds wallow in dust 

 for the purpose of ridding themselves of vermin. The reason 

 is doubtful, although the fact is notorious ; but it is certain that 

 these birds have vermin, of which they do not succeed in ridding 

 themselves by means of their bills or claws. If an active little 

 bird, like a chaffinch or wren, be not able to wield its bill effective- 

 ly, how much less chance has the spoonbill, the stork, the goose 

 or the eagle ! I have watched gannets as they sat on their nests, 

 or roosted on the rocks, but I never saw one scratch its head, 

 although these birds are sadly infested by insects, and have the 

 middle toe serrated. But against the supposed use of the ser- 

 rated claw in the goatsucker, the fact is decisive that birds at 

 least as much infested by insects, such as the magpie, auk, and 

 guillemot, have no comb. Besides, the claw in question is so con- 

 structed that it could not answer the purpose intended ; for the 

 serratures are close, and therefore could not act as a comb, or if 

 the barbs could be introduced between them, they are so thin 

 and delicate that a week's use would render the comb unservice- 

 able. As to the seizing of insects, it being a fact not observed 

 but supposed, it is only necessary to ask if herons, pelicans, and 

 boobies catch insects, or fishes either, with their claws ? Lastly, 

 if the pectinated claw be used by the goatsucker for cleaning its 

 whiskers, which become clogged with the scales of moths, why 

 has not the cormorant whiskers to be cleaned, seeing it has the 

 currycomb ? In short, we know nothing about the matter ; but 

 one fact often throw?:: light on another. 



Thus it is a fact that the edges of the bill of the gannet, the 

 booby, and the lesser booby, are irregularly serrated, sometimes 

 deeply and indistinctly, especially in the latter species. Thfe 

 serratures have a regular direction, being inclined inwards or 

 toward the base of the beak. Now, it is a fact, that until the 



