198 



Herr. L. Zehntner on the Development of 



an unjointed cartilaginous streak, which in the next stage 

 (fig. 1) is divided into two phalanges. We have thus also 

 in the fourth toe, at a certain period, the normal number of 

 phalanges, viz. three separate phalanges and a bit of carti- 

 lage which corresponds to two phalanges, into which it is 

 later split up. The first phalanx, however, comes into very- 

 near relation with metatarsale iv., and finally fuses with it, 

 before the claw-bearing phalanx is differentiated. In fig. 1 

 there is no longer any trace of this phalanx. To return to 

 fig. 2, the first phalanx of the second and third and the 



Fiar. 2. 



Fijr. 1. 



Fig. 3. 



Embryonic feet of Cypselus nielba. 

 Fig. 1. Of the eighth day. 



2. Of the tenth day. 



3. Of a stage rather earlier than in fig. 1 . 



first (really second) of the fourth toe are spherical, with 

 nearly even articular surfaces. The second phalanx of the 

 third toe is very short, broader than long, in fact disk- 

 shaped. This is the case to a greater extent with the second 

 phalanx of the fourth toe. The two terminal phalanges of 

 the three outer toes are much more slender and are all of a 

 similar form. 



The question now arises — What is the fate of the second 

 phalanx of the third and fourth toe ? In an embryo of the 

 12th day they are present, and even more conspicuous than 

 on the 10th day. In the third toe the phalanx in question 

 gets more quadrangular in form, in the fourth rounder. The 



