212 EMEU 



twentieth day the beak, furnished with the hard " egg -tooth," is 

 thrust through the inner shell membrane, and the bird begins to 

 breath the air contained in the chamber. Thereupon the pulmonary 

 circulation becomes functionally active and blood ceases to flow 

 through the umbilical vessels from and to the allantois. The latter 

 shrivels up, the navel becomes completely closed, and the chick by 

 repeated filing motions pierces the shell at the broad end of the egg 

 Avith its egg-tooth. A small crack in the shell is sufficient to destroy 

 the surprising strength of the intact egg, the chick casts off the 

 dried, now no longer useful, remains of allantois and amnion, and 

 steps out into the world. 



The length of the 'period of incubation seems to depend upon, first, 

 the state of perfection in which the young bird leaves the egg, the 

 Nidifugae requiring a much longer time than the Nidicol^ ; secondly, 

 the size of the bird, — large birds requiring more days than small 

 birds ; thirdly, climate and season, because an occasional slight 

 cooling of the eggs retards the development of the embryo. The 

 amount of cooling will naturally be greater in cold than in hot 

 climates, while the temperature of the sitting bird varies within 

 small limits only. However, there seem to be no observations 

 made on the question if there is a difference in the length of in- 

 cubation between polar and tropical individuals of the same 

 species. Experience with artificial incubators has shewn that 

 during the earliest days of incubation the growth of the embryo 

 can be much retarded or even be stopped temporarily by a tempera- 

 ture below the normal point ; on the other hand, a higher than 

 normal temperature does not shorten the time of incubation but is 

 rather detrimental to the embryo's life (c/. W. Evans, Ibis, 1891, pp. 

 52-93). 



EMEU, evidently from the Portuguese Ema,^ a name which has 

 in turn been applied to each of the earlier-known forms of Eatite 

 Birds, but has in all likelihood -finally settled upon that which 

 inhabits Australia, though, until less than a century ago, it 

 was given by most authors to the bird now commonly called 

 Cassowary. 



^ By Moraes (1796) and Sousa (1830) the word is said to be from the Arabic 

 Nddma or Ndema, an Ostrich {Stnithio camelus) ; but no additional evidence in 

 support of the assertion is given by Dozy in 1869 {Glossaire des mots espagnols et 

 portugais dirivis de I'arahe. Ed. 2, p. 260). According to Gesner in 1555 (lib. 

 iii. p. 709), it was the Portuguese name of the Crane, Grus comviunis, and had 

 been transferred with the qualifying addition of "di Gei" {i.e. Ground-Crane) 

 to the Ostrich. This statement is confirmed by Aldrovandus (lib. ix. cap. 2). 

 Subsequently, but in what order can scarcely now be determined, the name was 

 naturally enough used for the Ostrich-like birds inhabiting the lauds discovered 

 by the Portuguese, both in the Old and in the New World. The last of these 

 are now known as Rheas, and the preceding as Cassowaries. 



