560 The American Naturalist. [July, 
reproduce a perfect new individual. As we ascend in the ani- 
mal scale the power is confined to the reproduction of a lost 
part in the process known as recrescence. As you well know, 
in the group to which the frog and salamander belong, a limb 
or tail, or even a lower jaw may be reproduced. The only 
logical interpretation of these phenomena is that the heredi- 
tary powers are distributed in the entire protoplasm of the 
organism, and the capacity of reproduction is not exhausted in 
the original formation of the limb, but is capable of being 
repeated. There has been considerable discussion of late as to 
the seat of this power of recrescence. It seems to me not impos- 
sible that in the vertebrates it may be stored in the germ-cells, 
-and it would be very interesting to ascertain experimentally 
whether remoyal of these cells would in any way limit or affect 
this power; we know that such removal in castration or ovari- 
` otomy sometimes profoundly modifies the entire nature of the 
organism, causing male characters to appear in the female, 
and female characters to develop in the male. 
So far as man is concerned it has been claimed by surgeons 
that genuine recrescence sometimes occurs; for example, that 
a new head is formed upon the femur after exsection; but my 
friend Dr. V. P. Gibney informs me that this is an exaggera- 
tion, that there is no tendency to reproduce a true head, but 
that a-pseudo-head is formed which may be explained upon 
the principle of regeneration and individual transformism by 
use of the limb. | 
Pfliiger’s opinion is that recrescence does not indicate a 
storage of hereditary power, that there is no pre-existing germ 
of the member, but that the re-growth is due to the organizing 
and distributing power of the cells at the exposed surface, so 
that as new formative matter arrives it is built up gradually 
into the limb. This view would reduce recrescence to the 
level of the regeneration process, which unites two cut sections 
of the elements of a limb in their former order. It is partly 
opposed to the facts above referred to, which seem to prove the 
distribution of the hereditary power. Yet it seems to me quite 
consistent to consider these three processes—a, reproduction of 
a new individual from every part; b, reerescence of a new 
