POLES OF THE EGG. 37 



demonstrated in the egg of the common domestic fowl as in that 



of any bird.* If a per- oi 



fectly fresh egg (fig. 



20) is boiled hard and 



allowed to cool, at 



least until it may be c //j 



handled comfortably, 



and the shell (s) and 



white (a, a 1 ) carefully 



peeled off, the yolk 



(ol) will remain as 



a perfectly distinct Fig. 20. 



Fig. 20. Longitudinal section of a freshly laid Hen's egg, which has been 

 boiled, s, the shell; a, a 1 , the spirally wound layers of the "white"; ch, the 

 innermost layers of the " white " (albumen) twisted into cords, chalazce, which 

 serve as axles, upon which the yolk swings and revolves, whenever the egg is 

 rolled over, so as to keep the side with the white spot, cicatricula (c), uppermost ; 

 _y, z/ 1 , the outline of the yolk mass ; ol, the concentric layers of yolk ; v, u 1 , the 

 more fluid-like part of the yolk ; p, remnant of the germinal vesicle ; c, the 

 cicatricula. Original. 



* In my investigations of the character of the yolk of Turtles, a group of 

 reptiles which produce eggs most closely allied in character to those of birds, I 

 found an approximation to what occurs in the eggs of the latter. See my 

 observations to this effect in Agassiz's " Contributions to the Natural History of 

 the United States," vol. ir. 1857, p. 479, section V.; and note 1, p. 480, note 2, 

 p. 481 ; also Plate IX., fags. ll-ll h , and Plate IX d , fig. 2, with the descriptions 

 of the figures. 



Note on Scientific Property. It may, perhaps, surprise some of the readers 

 of this volume, upon turning to the "Contributions" mentioned in the above 

 note, not to find my name upon the title-page of the volumes which contain the 

 subjects referred to therein. This is no fault of mine, but of the editor of the 

 series, Professor L. Agassiz. In a little pamphlet entitled, "A Claim for Scien- 

 tific Property" I have published, with somewhat of detail, my claim to a part of 

 the substance of the second, third, and fourth volumes, and a right to have my 

 name upon the title-page of such volumes. It was well understood between 

 Prof. Agassiz and myself, as the result of several conversations, that my share 

 in the investigations should be clearly and distinctly set forth, so that I, in com- 

 mon with him, should be held responsible for the facts, ideas, theories, &c., as 

 far as the language so expressed them ; and in accordance with this understand- 



