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 hasa 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 vertebrz ; 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 
