ORGANS IN THE EMBRYO OF THE FOWL. 



117 



Condition of t/ic Allantois in Anamniotic Embryos. 

 The allantois is well formed in four of these embryos ; one 

 (No. 57) was too young to show it externally. It is obvious 

 that in the absence of the amnion the growth of the allantois 



FIG. 16. Experiment 60. Section along the line A-f>, Fig. 15. bl. , blastoderm 

 overlying the embryo; sow, somatopleure ; spl., splanchnopleure. On the right side 

 there is a break in the continuity of somatopleure and splanchnopleure ; this was evi- 

 dently produced in the preparation, as the continuity is perfect some distance in front, 

 and also behind. 



must be attended with difficulties. When the amnion is normally 

 formed a large free space is created above and around it, into 

 which the allantois can freely spread. The absence of this space 

 causes compression of the allantois, and changes the direction of 

 its growth, but I do not think that the latter is much impeded. 

 The mechanical force of the expansion of the allantois causes 

 separation of the somatopleure and splanchnopleure to proceed 

 more rapidly in its immediate vicinity than elsewhere (see Fig. 

 15). In experiment 124 the greater diameter of the allantois 

 exceeds the greatest length of the embryo. I see no reason why 

 this process might not provide all necessary space for its expan- 

 sion. It might be, however, that the resistance offered would 

 tend to cause accumulation of the products of excretion in the 

 body of the embryo, and thus gradually poison it. 



2. Experiments on the Tail -Fold of the Amnion. 

 I have also made a number of experiments on destruction ot 

 the tail-fold of the amnion. The results are in most cases com- 



