1921] WELLS—ZOOCECIDIA 363 
RoTIFERA (pl. XXI).—Only one rotifer gall is known. It con- — 
sists of simple enlargements of the ends of filaments of Vaucheria (1) 
which harbor at their center the cecidozoon. weed are to be 
regarded as extremely simple kataplasmas. 
CopPEPODA (pl. ned —Represented by one form only, : a simple 
kataplasma (1). ~ 
NEMATODA (pl. XXI).—Represented by two genera, one using 
the roots (x), the other the aerial parts (2), producing simple 
kataplasmas in both instances. The root inhabiting form pro- 
duces the greatest modification. 
ACARINA (pl. XXI).—These galls are chiefly the work of the 
members of the genus Eriophyes. Two fundamental lines of 
evolution are evident: the production of numerous aborted parts 
(kataplasmas) from stems, buds, and leaves (1, 2); and a leaf 
gall line beginning with the erineum (mat of trichomes) stage (3) 
and passing into the diverticulum condition (5) or the leaf edge- 
roll state (6). From the leaf blade the erineum-forming type 
may change its point of attack to the rachis or petiole with more 
or less hyperplasia and hypertrophy of the hypodermal cells. 
Such an unusual form is seen in (4). The shallow diverticulum 
has given origin to the elementary prosoplasma leaf types as repre- 
sented by (7-10). The figures with their connecting arrows are 
self-explanatory. It is believed that a type like that shown in (9), 
which is devoid of trichomes, has been derived from the trichome- 
bearing kinds. The prosoplasmas of the Acarina are of the simplest 
variety. In the entire absence of sclerenchyma layers and in the 
non-deviation from the primitive pouch type they constitute as a 
group the lowest of the prosoplasmas. 
OrtTHoPTERA (pl. XXI).—Only one genus is represented (1), 
forming an. ee kataplasma consisting of aborted stem 
and leaves. 
NeEvrRopTERA (p]. XXI).—A simple coftical swelling constituting 
a very primitive kataplasma (1) is only reported for this group. 
THysANopTerA (pl..XXI).—These tropical galls are all of the 
kataplasmic type, the most primitive of which is the simple leaf 
fold (x), from which the more specialized condition shown in (2) 
has been derived. A simple curled edge probably represents 
