HOMCOSIS 133 
by a few marked variations, each of which occurred 
simultaneously in all the feathers at once, several 
serious difficulties are avoided, and on the analogy of 
similar known cases we have every reason to believe 
that this was so. And similar changes may take place 
in cases where the pattern depends on the coloration 
of a group of feathers or hairs. Indeed, if we con- 
sider, we shall find it very difficult to picture such a 
process as taking place in any other way. We can 
scarcely suppose the spots of the leopard, for instance, 
to have arisen one at a time. 
An important kind of discontinuous variation is 
that to which Bateson has applied the term homeosts. 
The same sort of change had previously been described 
by Masters in the case of plants under the name 
‘metamorphy,’ but the latter expression has also 
been employed in other senses. Homeeosis consists 
in the assumption by one member of a meristic series 
of the form or character proper to another member 
of the same series ; for example, the modification of 
the petal of a flower into a stamen, or of the eye of a 
crab into an antenna-like organ. 
‘In these cases a limb, a floral segment, or some 
other member, though itself a group of miscellaneous 
tissues, may suddenly appear in the likeness of some 
other member of the series, assuming at one step the 
condition to which the member copied attained pre- 
sumably by a long course of evolution.’ * 
The phenomenon of homeeosis is frequently to be 
seen among the parts of flowers. Double flowers in 
* ‘Materials for the Study of Variation,’ p. 570. 
