STRUCTURE OF EGGS. 113 



impossible to balance an egg on its larger end while 

 the membranes within remain unbroken, though this 

 may be readily effected by violently shaking the egg 

 till the membranes be ruptured *. 



This mechanism, simple and admirable as it is, 

 results, according to M. Dutrochet, from the nature 

 of the previous relations between the situation of the 

 egg in the egg-organ, the position of the broad ex- 

 tremity of the egg-tube, and its general form. The 

 egg presents to the mouth of the tube that part of it 

 which is opposite to the germ. The mouth of the 

 tube being placed laterally, transmits the egg in the 

 same position in which it received it, that is to say, 

 with the germ placed on the equator of the yolk, the 

 axis of which is nearly in the direction of the egg- 

 tube ; and this is so formed that its axis is not quite 

 the same as the axis of the yolk. 



It follows from the preceding observations of 

 M. Dutrochet that the embryo chick contained in the 

 germ has no organic connection with its mother. 

 It does not adhere to the proper membrane of the 

 yolk, and the yolk does not itself adhere to the vas- 

 cular membrane in which it is contained. This 

 accords with what is generally observed in the vege- 

 table kingdom, the germs of plants from the instant 

 of their appearance being like greenish white points, 

 devoid of all connection with their capsules, and con- 

 sequently with the seed organs (pvaria). M. Du- 

 trochet was the first to demonstrate, that the egg 

 contained in the pouch of the egg-organ has but one 

 proper membrane under which the substance of the 

 yolk lies loose; -an observation which overturns 

 Baron Haller's theory respecting the existence of 

 the chick previous to fecundation, supported as it 

 was on the solitary fact of an egg on which a bird 

 had sat, exhibiting a portion of intestine enveloping 

 * Ornithology, by Ray, p. 11. 



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