114 Phenomena Refuting Simple Epigenesis 
Nevertheless some other varieties of omphalosite 
monsters seem to show that the presence of any part 
whatever of the vertebral axis is sufficient to permit 
at least partial development; for instance in the cephalic 
monsters the embryo consists generally of the head 
alone.*7 We note however that these monsters com- 
monly contain the anterior extremity of the spinal cord 
which can have been only slightly differentiated in the 
embryonic stage at which the incomplete development is 
arrested. In some of these cephalic omphalosite mon- 
sters, a large part of this anterior extremity of the spinal 
cord may even have undergone a process of reabsorption 
after the previous arrest of the partial development. 
As we shall see soon Born succeeded in producing 
artificially a thing like these cephalic omaphalosite mon- 
sters by grafting upon a complete tadpole a piece removed 
from another tadpole, and consisting only of the head 
and a small part of the elongated medulla. 
Concerning the double monsters with double sym- 
metry, it will be worth while to repeat once more in 
extenso the following statement of Roux, even though 
we have reported it already, for the most part, in the 
preceding chapter: 
“This additional fact speaks directly against the 
achievement of development of the individual through 
a general, reciprocal, formative cooperation of all parts 
to form a whole; namely that in the chief class of double 
monsters, and so in those double formations which cor- 
respond to the law which I formulated of the double 
symmetry of the anlagen of organs, the piece absent 
in a symmetrically similar way from each of the two 
™Dareste: Recherches sur la prod. artif. des monstr. P. 498. 
