142 Remarks on Incubation, 



membranous sac situated internal to the external thick one. 

 This animal has one common sac, and thus differs from the 

 orang-utan, which has two ; the lungs also differ from those in 

 the orang-utan * in being subdivided on each side, the right 

 lung having three, the left two lobes, as in the human sub- 

 jectf The extremities of the bones of the animal were car- 

 tilaginous. 



London, January, 1832. 



Art. V. Remarks on Incubation, in reference to those expressed 

 in Professor Rennie's Edition of^^Montagus Ornithological Dic- 

 tionary.'' By Charles Waterton, Esq. 



" I most earnestly entreat my readers to weigh ewery fact, and rigidly 

 scrutinise every inference." (See the Professor's "Use of System," 

 p. xxi. in said Dictionary.) 



The Professor tells us, in the last Number (p. 101.) of 

 this Magazine, that " the terns, &c." (this " &c." is very 

 vague) " leave their eggs for whole days together." In his 

 " Plan of Study," he informs us that the careful dabchick 

 covers her eggs with a quantity of dry hay, mind, reader, to 

 keep them *marm till her return. 



Now, the dabchick lays her eggs at the same time of the 

 year that the terns lay theirs. The eggshells of the dabchick 

 and of the tern are of the same thickness, as near as may be, 

 and their contents are precisely of the same nature. If, then, 

 the ^^<g of the dabchick requires to be covered in order to 

 keep it warm when the bird leaves the nest, that of the tern 

 requires the same precautionary measure, for the same reason. 

 Or, vice versa, if the egg of the tern be left uncovered for 

 whole days together, then, by a parity of argument, the egg 

 of the dabchick might be left uncovered for whole days toge- 

 ther. But the Professor tell us expressly, that, if the dabchick 

 quits her eggs for a moment without covering them, their 

 vicinity to moist plants, or to water, would certainly prove 

 fatal to the embryo chicks. 



From these two extreme statements of the Professor, first, 

 that the terns leave their eggs uncovered for whole days to- 

 gether ; and, secondly, that the dabchick covers her eggs with 

 dry hay, if she leaves the nest for a moment, as their vicinity 



* See Mr. Owen's dissection of the Orang-utan, in No. I. of the Proceed- 

 ings of the Zoological Society of London. 



\ The larynx and a portion of the ulcerated intestine have been depo- 

 sited in the museum of the Royal College of Surgeons in London. 



