6 FREDERICK S. BREED 



light in the same way. I follow my notes: " Made at times 

 a regular clicking noise with breathing. Frequently clapped 

 mandibles together. Repeatedly raised bill with a 



lifting motion of the head. This reaction might bring tip of 

 bill, and hence the bill scale, in contact with the shell. Opened 

 mouth and lifted bill. Eyes closed while in egg. Sometimes 

 pushed bill forward, following this movement with a clapping 

 together of the mandibles." 



While the chicks were still in the egg the legs were folded 

 well up on the breast and the head was turned down toward 

 the breast. After the egg was chipped so that the behavior 

 of the animal could be observed, the lifting movement of head 

 and beak above referred to was more frequent than any other. 

 One much less often saw anything like a forward thrust of 

 the bill. 



The chicks came out of the eggs wet and, in a temperature 

 of 103° F., remained several hours before drying off. Spells of 

 vigorous activity alternated with periods of passivity during the 

 chicks' struggles just prior to hatching, as well as for some 

 hours after hatching. The post-embryonic life of the chick in 

 its early hours seemingly prolonged without interruption the 

 life in the embryo. Chicks appeared to break the shell in two 

 by a lifting, struggling movement of the head accompanied by 

 a stretching, straightening movement of the legs. At least I 

 have observed this combination of movements at the moment 

 of hatching. Now if one watch carefully the behavior of a 

 chick for some time after exclusion, he finds that there are these 

 similarities between the later life within the shell and the earlier 

 life outside the shell. The positions of the head and legs within 

 the shell correspond to the positions assumed by these members 

 during the passive states shortly after hatching. In both cases 

 activity and passivity alternate, the iDeriodicity of which alter- 

 nation seems to be largely determined by intra-organic stimuli. 

 If it be true that the legs participate in the action that finally 

 breaks the shell, as I think they do, the lifting of the head and 

 the pushing with the legs would be represented in the early 

 post-embryonic life by those pulses of activity in which the 

 chick lifts its head, rises to its feet, staggers a few steps, or 

 struggles a few moments, and lapses again into the passive state. 

 And just as the chick in the shell often claps its mandibles 



