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of double monsters in fishes, found that one was always weaker than the 
other and that the weaker was attached to the ventral belly-wall of the stronger. 
His observations extended from the fifth to the thirteenth day of development. 
BERNHARD SCHULTZE ?! denied that an unbroken series of monsters could 
be produced. He separated duplications of the axial organs from those of 
the extremities or other external or internal organ groups. According to him 
the double monsters characterized by a duplication of the axial organs, are 
to be considered a single individual, not two, and the more complete the 
duplication the greater the deviation from the normal. The time at which 
duplication starts is when the embryonic area appears. He maintains that 
the formation of a double axis cannot be considered as cleavage or budding, 
but that it must be looked upon as elementary and the conditions necessary 
must be present before the formation of the embryonic area. The predisposition 
of some women to monstrosities points to the fact that the conditions governing 
the abnormal peculiarities are present in the ovaries. He conjectured, as did 
Simpson 2? somewhat earlier, that such ova are characterized by a double 
germinal area and as a result of this anomaly a double embryonic area is 
formed. 
Reicuert ”? had occasion to study three bird monsters and one crayfish 
monstrosity. In the bird monsters, he defended Meckkr’s views. He separates 
monster formation into two classes, that in which the cleavage is longitudinal 
and that in which the cleavage is transverse. In either class it is impossible 
to distinguish the ovum from a normal egg during the early stages. The 
vegetative protoplasm completes its segmentation in the regular manner; 
then follows the embryonic cleavage that stands on the same footing as the 
creative process. His crayfish monstrosity consisted of two individuals fused 
at their caudal extremities. 
Forster ?* on the other hand recognized a longitudinal cleavage only 
and denies the probability of a transverse division. Dénirz ?* contradicts this 
after his study of a double embryo chick in which the heads were united 
and the caudal ends directed in opposite directions. He, like REICHERT, 
defended both longitudinal and transverse cleavage. Monsters with duplicated 
extremities he does not consider as double monsters, but monsters with ab- 
normal organologic growth. Several have tried to clear away the uncertainty 
of transverse cleavage by considering it a rotation of parts of the longitudinal 
division. According to SCHEUTHAUER,?® cleavage must begin before the formation 
of the neural groove; the rotation that follows is due to the contraction of 
the diverging parts still adherent at one point, the amount of rotation depending 
apparently upon the amount of contraction. Dirrmer *7 concluded that originally — 
the two embryos lie parallel to each other; with the elevation of a neural — 
plate a rotation occurs whereby both longitudinal axes appear in a straight 
line. The causes of rotation are the broadening of the embryonic anlages 
and the elevation of the neural plates. AuureLo ** observed three monstrosities: 
(1) a chick of about thirty six hours incubation cleft caudally with the parts 
at an angle of about 120°; (2) a chick of about 90 hours incubation with two — 
separate bodies, with heads close and tails widely separated; (3) like second, — 
but older. He believed as above, but thought in addition that a most important — 

