The last of Butler's biological writings is the Essay, "THE DEADLOCK
IN DARWINISM," containing much valuable criticism on Wallace and
Weismann. It is in allusion to the misnomer of Wallace's book,
"Darwinism," that he introduces the term "Wallaceism" {0d} for a
theory of descent that excludes the transmission of acquired
characters. This was, indeed, the chief factor that led Charles
Darwin to invent his hypothesis of pangenesis, which, unacceptable as
it has proved, had far more to recommend it as a formal hypothesis
than the equally formal germ-plasm hypothesis of Weismann.


The chief difficulty in accepting the main theses of Butler and
Hering is one familiar to every biologist, and not at all difficult
to understand by the layman. Everyone knows that the complicated
beings that we term "Animals" and "Plants," consist of a number of
more or less individualised units, the cells, each analogous to a
simpler being, a Protist--save in so far as the character of the cell
unit of the Higher being is modified in accordance with the part it
plays in that complex being as a whole. Most people, too, are
familiar with the fact that the complex being starts as a single
cell, separated from its parent; or, where bisexual reproduction
occurs, from a cell due to the fusion of two cells, each detached
from its parent. Such cells are called "Germ-cells." The germ-cell,
whether of single or of dual origin, starts by dividing repeatedly,
so as to form the PRIMARY EMBRYONIC CELLS, a complex mass of cells,
at first essentially similar, which, however, as they go on
multiplying, undergo differentiations and migrations, losing their
simplicity as they do so. Those cells that are modified to take part