214 



CHARLES R. STOCKARD 



apart on the blasto-disc. Such an interpretation would certainly 

 seem proper in the case of the fish and the bird. 



The third case, that of the separate twins, plate 4, differs from 

 the others in that both babies are deformed. Yet the deformities 

 and other peculiarities of this case make it unique in value. It 

 has been seriously questioned, on the basis of psychological and 

 other studies (Thorndyke '05), whether actual cases of human 



A 



28 



B 



Fig. 28 Drawings of the ventral surfaces of the hands and feet of the iden- 

 tical human twins shown in plate 4. A, from one individual, and, B, from the 

 other. The four hands are all polydactylous, having an accessory finger on the 

 ulnar side, and the four feet are similarly polj'dactylous, all having an accessory 

 toe on the fibular side. The polydactylism is practically identical in the two 

 individuals. 



identical twins do exist. The structural conditions of the two 

 male twins in this case renders it practically certain that they 

 arose from a single fertilized egg. There are six fingers on each 

 of the four hands, as shown in plate 4, and more distinctly in 

 figure 28 A and B; there are also six toes on each of the four 

 feet, as the illustrations show. Such a polydactylous condition 

 is known to be derived from a peculiar germinal complex and is 

 not produced by the developmental environment. The chance 

 is one against thousands that two fertilized eggs carrying exactly 



