Arteries in Monsters of the Dicephalus Group 



465 



stage is represented by a two-headed turtle, Teras XX. Its gross anatomy 

 has already been described and needs no repetition. The blood vessels 

 in this organism were followed with some difficulty, owing to the small- 

 ness of the specimen and the fact that the blood vessels were not injected, 

 and the animal had been preserved by being thrown alive into alcohol of 



Text Fig. 3. Diagram showing the transformations in the primitive 

 arterial arches in Teras XV. 



unknown strength before it came into the hands of scientific persons. 

 Although phylogenetically Teras XX is more primitive than the other 

 specimens studied, its position in the cosmobiotic series is not altered, 

 for cosmobia are not limited to any one genus and species, the qualities 

 involved being applicable to all vertebrates. 



The duplicating tendency has progressed so far in this specimen that 

 not only the heads, but also the necks are entirely separate and distinct 



