DICHOTOMY. 125 



is still further arrested, with nothing but a confused con- 

 glomeration of tissues and organs, without any definite 

 shape to guide the observer, there is often more difficulty 

 in coming to a conclusion. Shapeless masses of this 

 character containing elements of a second embryo in 

 the form of a tumour consisting of bone, liver, teeth, 

 intestines, digits, and the like, are known as teratomata. 

 Many such have been described in human beings. A 

 few examples have been recorded in calves. 



Up to this point we have been concerned with anterior 

 and complete dichotomy : now posterior dichotomy of 

 the trunk claims consideration. A simple case is 

 furnished in the green lizard (Lacerta viridis) shown 

 in fig. 69. The animal has a bifid tail. To show that the 

 bifidity is not due to injury and subsequent reproduction 

 of the tail and consequent budding, it may be mentioned 

 that reproduced tails are never so perfectly conformed as 

 in this specimen and do not contain vertebrae ; further, 

 monstrous lizards have been recorded in which the 

 cleavage had involved the trunk so as to produce the 

 bodies and limbs of two lizards but only one head. In 

 one specimen described and figured by Tiedemann, a 

 double-bodied monstrous green lizard has a double, but 

 fused head. 



Passing from tailed animals, such as lizards, and 

 turning to frogs, it must be clear to every one that if 

 dichotomy occur, it need only be slight to produce re- 

 duplication of the pelvis with the limbs and associated 

 parts. This is a matter of interest because many 

 specimens have been incorrectly interpreted on account 

 of this fact not being properly appreciated. It is also 



