THE OOLOGJST. 



63 



CONTINUED FROM PAGE 59. 



pressure from the sides of the shell, under 

 the principle that the same body always oc- 

 cupies the same space, whatever shape it 

 may assume. Now, the chick being thus 

 positioned, a movement toward the ends of 

 the shell will release the head, which lies 

 t6ward the greatest width of the egg, from 

 the confined position, sufficient to enable it 

 to make use of its bill, Avhich, instead of 

 being iised instinctively for fracturing its 

 prison, is employed vigoi'ously as what the 

 author calls its "• birth throe," and the ex- 

 tremities of the body, acting as a fulcrum, 

 in connection Avith the movement of the 

 head, tends to produce a rotary motion, 

 which, if persisted in, completes the circuit 

 of the shell in due time. Thus Mr. Cleve- 

 land reasons. The gist of his arguments 

 as seen, is the release of the chick by its 

 struggles and its efforts to free itself from 

 the onus of birth, and the support of the 

 conviction of the rotary motion and uncon- 

 nected situation of the embryo. 



Though Mr. Cleveland's arguments are 

 evidently the issues of examination, and 

 founded for the most part on fact, we would 

 beg leave to make a few remarks upon the 

 subject, some of which, perhaps, do not co- 

 incide with his views. In the first place, 

 the shell is not ahvays fractured entirely 

 round, a point clearly overlooked ; neither 

 is there any rule for the position of the en- 

 tire rupture. Herein lies a point which 

 nearly invalidates both Mr. Marot's and 

 Mr. Cleveland's affirmations, Avhereas if the 

 shell is not ruptured roimd the circumfer- 

 ence, the chick does not rotate, and if the 

 embryo does not rotate, Mr. Cleveland has 

 lost his main point. Nothing is mentioned 

 in Mr. Marot's assertions of the direction 

 of the fracture, but it is to be inferred from 

 the engraving, that it agrees with the dec- 

 laration of the former gentleman. Mr. 

 Wolff says, " The bill of a chick will al- 

 ways be found near tlie middle of the shell. 

 Hence, as a hole at that point weakens the 

 shell, the fracture will be made, each way, 

 from the hole." This, as we understand it, 

 signifies that the fracture is made at one 



point, and is extended by other means than 

 by the point of the beak, M^hich certainly 

 doesn't imply that the bird rotates. Why 

 does not Mr. Cleveland contradict this ? If 

 a person interested will examine a dozen 

 eggs, that are about to burst, he will find 

 in nine cases out often, that no two frac-' 

 tures are extended alike ; moreover, he will 

 notice that but one point in the entire shell 

 bears the marks of the chick's bill, and if 

 the egg is opened after the hole is commenc- 

 ed, and before the bird makes its exit, a 

 quick glance will show the bill of the chick 

 opposite, or very nearly opposite, the hole, 

 as often to the left as to the right of it. 



In the second place, both Mr. Marot and, 

 Mr. Cleveland are wrong concerning the at- 

 tachment of the body to the membrane of 

 the shell. Such an attachment does occur ; 

 and this attachment is broken before the 

 chick leaves the shell. The membrane is 

 a tough lining to the inside of the shell, and 

 contains blood ; this blood is conveyed by 

 means of small vessels or chords, to and 

 from the body, which until the chick is 

 ready to make its exit, remains attached to 

 them ; how a bird can rotate tivice in the 

 shell, as Mr. Cleveland asserts, with this 

 membrane attached to it, is unknown to us. 

 Tlie chick's head is placed under the right 

 wing, and as Mr. Marot says, the hole is 

 chipped, and not bored. Thirdly, it cannot 

 be. said that the chick does not expand. 

 The air chamber, which at first does not 

 contain over a fifth of a cubic inch of air, 

 at the time of the chick's first attempt at 

 release, is enlarged to from three to five 

 times its original capacity, by the permea- 

 tion of air throng] 1 the shell, and which, be- 

 ing composed mainly of oxygen, supplies 

 the eml)ryo with means of living until its 

 exertions liberate it. The inhalation of air 

 by the chick^ not only produces a moment- 

 ary expansion, but, being its nourishment, 

 it aids the growth of the bird, which is very 

 rapid, and at the period of its evacuation 

 has attained such size that with the aid of 

 its beak and its struggles, it rends the 

 membrane, if not too tough, and breaks 

 the shell asunder. 



