342 STUDIES IN GENERAL PHYSIOLOGY 
that observed among the Chetopods or Pantopods. On the 
other hand, the leech is not much more capable of regenera- 
tion after an injury to its body than the human being; both 
can only cover the amputated stump with skin. If one wishes 
to utilize the power of regeneration of animals for phylo- 
genetic purposes, this can be done only for members belong- 
ing to one and the same morphological group. According 
to Sachs, only “the forms of the same group may be con- 
’ sidered related to each other; they have nothing in common 
phylogenetically with the members of another group; every 
morphological group is, so to speak, a plant kingdom in 
itself.”’? 
But whether even within the same phylogenetic group, 
in the sense in which Sachs uses the term, the power of 
regeneration of a species is a simple function of its position 
in the group can at present, from lack of facts, not be decided. 
My experiments on the functions of the brain in worms 
showed that no parallelism exists between these functions 
and the systematic position of each species. Much less does 
such a parallelism exist in regard to the tropisms which can 
be altered comparatively easily through external conditions. 
But though it is not correct to say that the power of regener- 
ation decreases the higher the animal stands in the system, 
it is perhaps true, that the number of species capable of 
complete regeneration is relatively greater in the groups of 
the Coelenterates and worms than in the groups of Arthro- 
pods and vertebrates. 
3. In general, it will also be found correct that the power 
of regeneration is greater in the embryo than in the adult 
animal. The young larva of the frog regenerates an ampu- 
tated leg, while this is not possible in the adult animal. 
Those who assume that the power of regeneration is the 
greater the lower the position of the animal in the natural 
1J. von Sacus, Flora, 1894, p. 219. 
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