DEVELOPMENTAL HAZARDS OF HUMAN TWINS 153 



3. Acardii acephali, which possess a body and at least 

 some of the extremities fairly well developed, but no 

 head (Fig. 53). 



Fig. 53. — A pair of one-egg human twin fetuses attached to the com- 

 mon placenta. The one on the left hand is headless and has a dead 

 heart. It is an example of the type of twin known as acardius acephalus. 

 (After Schatz.) 



4. Acardii amor phi in which the whole organism is 

 a shapeless, rounded mass with only traces of head and 

 appendages (Fig. 54, p. 154). 



There are various more or less well-defined types of 

 acardii amorphi, distinguished by various vascular 

 peculiarities. 



One of each of these types of acardii is shown in the 

 accompanying figures. Some of them, especially the 



