1921] WELLS—ZOOCECIDIA 375 
germ plasm dominates, while in its later stages (prosoplasmas) 
the animal’s germ plasm gains control; the whole, however, con- 
stituting a single progressive series of factorial transformation as 
far as the changes in the animal germ plasm are concerned. 
Summary 
1. Kiister’s groups, kataplasmas (lower galls of indefinite 
nature, differentiation conditions similar to, but in complexity 
below that of normal plant) and prosoplasmas (higher galls of 
definite nature, differentiation conditions new) are basic for the 
present paper. 
2. Evolutionary concepts are introduced in pointing out that 
prosoplasmas have arisen from kataplasmas. The probable main 
outlines (phylogenetic trees) of the natural cecidozoon gall groups 
are presented for the first time. 
3. Kataplasmic evolution is held to be a process of progressive 
inhibition of differentiation ending with tissue homogeneity. 
Prosoplasmic evolution may only begin when homogeneity has 
been attained, and consists in the development of new form and 
tissue orientation characters chiefly. In prosoplasma formation, 
whether viewed ontogenetically or phylogenetically, the insect 
larva has gained control of the differentiation and morphogenetic 
mechanisms, so that animal factors come to expression in plant 
tissue. 
4. Origin of significant characters of prosoplasmas lies in change 
in eee situation in animal’s germ plasm. | 
NortH CAROLINA STATE COLLEGE " 
RALEIGH, 
LITERATURE CITED 
1. BreverInck, M. W., Uber Pflanzengallen. Bot. Zeit. 35:17-23. 1877. 
2. Cook, M. T., Galls and insects Aiba sei Ohio Naturalist 2: 263- 
278. 1902; 3:419-436. 1903: 4: 115-147. 
3. CoseEns, A., A contribution to the diiechiclegy and biology of insect galls. 
Trans. Cenudian Inst. 9:297-387- pls. 12. 1912 
4. Cosens, A., and Srvcrair, T. A., Aeriferous tissue in willow galls. Bor. 
5. Fett, E. P., Key. to American insect galls. N.Y. State Mus. Bull. 200, 
pp. 310. 1918. 
