0U7' Knowledge of the Indicatoridse. 3 



firm hold of the bird it wanted to throw out. This pre- 

 sumption is doubly feasible when nests in holes of trees, 

 such as those of Woodpeckers, Barbets, &c., are taken into 

 consideration, as in these instances the method employed by 

 young Cuckoos of working themselves under their victims 

 and so ejecting them would not be of the slightest use. As 

 all eggs discovered were in nests of this description it would 

 appear that our explanation is not without reasonable founda- 

 tion. These tooth-like appendages measure 1*8 mm. in 

 total length, the ^^^ojecting portioii of the top tooth being 

 0"9 mm. and that of the bottom one 0*5 mm., and are situ- 

 ated at the extremity of the beak ; the superior aspect of 

 the top tooth being prolonged slightly above the surface of 

 the premaxilla, while the inferior aspect of the bottom one is 

 slightly projected beyond the lower level of the mandible, 

 both having the distinct appearance of being welded on to 

 the ends. They overlap one another, thus enabling the bird 

 to obtain a very sure hold of anything it applied its beak to. 

 These hooks are semi-transparent and appear to be an 

 exaggeration of the shell-breaking scale which occurs on the 

 beaks of chickens, — thus being epiblastic in origin, whereas 

 the teeth of Odontornithes and Archceopteryx were true teeth 

 and consequently partly epiblastic and partly mesoblastic in 

 origin. It will thus be seen that the teeth of the ancient 

 reptile-like ancestors of modern bird-life, and the projections 

 on the beak of the nestling Indicator, are in no way related ; 

 consequently it does not appear like a case of reversion, and 

 would seem more after the nature of a subsequent develop- 

 ment engendered by the bird's habits of life. 



The photograph (Plate I.) shows plainly what we have 

 tried to describe. This was taken from a young Indicator 

 variegatxis (now preserved in formalin) found in a nest-hole 

 of Petronia petronella (Diamond Sparrow) on the 12th of 

 November, 1905. The adult Indicator was seen in the tree, 

 and no young Sparrows were found in the nest. Although 

 large (the nestling measures 90 mm. in total length), we 

 presume it developed quickly after the manner of young 

 CuckooS; and should judge its age as not more than ten days 



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