^"'ioi^^ 1 Shufeldt, E^gs of Rep/i/e.'; and Birds Compared. 227 



riir places selected by existing reptiles (if all kinds wluTcin to 

 deposit their eggs are not nearly as well known us in the case of 

 birds ; still, we are more or less familiar with their habits in this 

 respect in the case of many species. Often they are deposited 

 on the bare ground, and not in any way concealed or covered 

 over. Some dig down into the earth, depositing their eggs in the 

 excavation thus made, and then cover them over with the loose 

 dirt and other debris thrown out, as in the case of the crocodiles. 

 In certain American species, however, as in the alligator, another 

 method is resorted to, for it forms a hillock by itself, and this it 

 hollows out, filling the excavation with dead and decaying 

 vegetable matter, including leaves. In this the eggs are hatched 

 out by the sun and the heat generated through the decomposition 

 of the aforesaid vegetable matter. This habit must not be con- 

 trasted with the nidification of certain of the MegapodiidcB as 

 evidence that the latter occupy a low position in the system among 

 birds ; although, as an interesting fact, it would at first appear to 

 be so, especially as the Crocodilia — as in the case of many other 

 reptiles — lay perfectly ellipsoidal eggs, as do some of the Mega- 

 podes likewise (fig. 3, Plate XXXVII.) Here, however, the form of 

 the egg most assuredly may point to the common origin of the two 

 great groups in question — Aves and Reptilia ; whereas the method 

 of nidification would not, as I say, point to the fact that birds 

 practising it were of a low order of organization, or that they 

 would, in other words, present an unusual number of reptilian 

 characters in their morphology, which, as we well know, is not 

 the case with the Megapodiidce. 



Apart from this, it is fair to presume that the appearance of 

 spherical and ellipsoidal eggs among birds is, upon the other hand, 

 another hnk in the evidence of the proof that Aves and Reptilia 

 had a common origin in time. This fact has also been touched 

 upon by Heilmann in his recent studies of the subject.* 



As is well known, some birds lay more or less spherical eggs, 

 and of this class the Owls are a good example. Indeed, one of 

 the roundest eggs I ever examined was laid by a Barred Owl 

 {Strix V. varia), collected by Mr. Edward J. Court, but at this 

 writing in the Museum of Natural History at Los Angeles, 

 California. Mr. Court generously presented this specimen to Mr. 

 A. B. Howell, of Covina, California, and from him, I believe, it 

 passed to the above-named museum. While it was in Mr. Court's 

 possession I made a negative of it, and a photograph from that 

 is here reproduced in fig. 2 of Plate XXXVII. ; it is natural size, 

 and comes extremely close to being a perfect sphere. 



* Heilmann, Gerhard, " Vor Nuvaerende Viden om Fuglenes Afstamning." 

 Dansk Ornithologisk Foreuiiigs Tidsskrifl, gde Aargang, Haefte i, Copen- 

 hagen, Okt., 1914, pp. 12, 13. This admirable work, now appearing in parts, 

 on "Our Present Knowledge of the Origin of Birds," is of the greatest 

 value ; and it is my intention, when all the parts are out, to do it in English. 

 Part iv. has already appeared, and the work will probably be completed by 

 the summer of 1916. 



