1921] .WELLS—ZOOCECIDIA 359 
plasm (meristem); (2) gall characters are the result of the influence 
of both the plant and the animal, chiefly the plant in the lower 
galls and chiefly the animal in the higher galls. In connection 
with the first interpretation, KtsTer (10) expresses his astonish- 
ment at the multiplicity of the possibilities possessed by the 
cells composing the leaves. This consideration of the exceptional 
normal forms does not enable him to foresee this multiplicity, and 
throughout his writings there is the same emphasis. The plant 
cells are loaded with reaction possibilities, due, as KtsTER intimates, 
to the retention of an array of latent characters acquired in the 
course of evolution. His example of the Adelges gall on spruce as 
being similar to the normal cone of Sciadopitys is a case in point. 
- Cosens and Sincrair (4), in a study of certain willow galls, 
present a similar interpretation. They say ‘The reinstatement in 
a gall of vestigial characteristics of the plant has an important 
bearing on the question of gall formation.’’ They recognize, 
however, “a directive control over the activities of the protoplasm 
of the host’’ on the part of the cecidozoon, the result of which is 
referred to as an ‘‘environmental modification.”” The force of 
_ this recognition is weakened by their final statement that “there 
remains no authentic instance of any organ or tissue in a gall that 
is new, ontogenetically or phylogenetically, to the host.” 
With regard to the second interpretation, although a number 
of European writers, ADLER, FocKEU, and others, have recognized 
the essential “independence” of the higher galls (prosoplasmas of 
KUsTEr), they have not gone so far as to formulate any definite 
conceptions of gall phylogeny; only the recognition of the fact 
that certain galls show characters which could not possibly have 
sprung from the plant has been given. 
For the introduction of some genuine phylogenetic theories we 
must refer to Coox’s (2) study, which gives such statements as the 
following: 
The morphological character of the gall depends upon the genus of the 
insect producing it rather than upon the plant on which it is produced. The 
families show parallel lines of development from a low form up to a high form. 
The Acarin may be considered the lowest group of galls, the Aphidid the 
hext higher, the Cecidomyia galls the next higher, and the Cynipidous galls 
he highest. However, many of the Cynipidous galls are lower than. the 
Aphidid galls. 
