PORIFERA, COKLENTERATA, VERTEBRATA 75 
(2) Goette (1886) maintains that the gemmule con- 
sists of cells from several germ layers; (3) Carter 
believed at one time that the gemmule was made 
up of only one kind of cell; and (4) several 
authors (Marshall, 1884; Wierzejski, 1886; Zykoff, 
1892; Weltner, 1892) believe that a number of 
cells belonging to several classes are concerned in 
the origin of the gemmule. 
Evans (1900) has described in detail the formation 
and structure of the gemmules of Ephydatia blembin- 
gia. In this species the first sign of the formation of a 
gemmule is the presence of “single cells or groups 
of cells scattered about chiefly in the dermal mem- 
brane; the strands of tissue which support the dermal 
membrane; and in the tissues situated immediately 
below the subdermal cavity” (p. 89). No mitotic 
figures were discovered in these cells and conse- 
quently the reproductive part of the gemmule is 
probably not derived from one mother-cell. These 
cells wander “through the dermal membrane, and 
strands of tissue which support the membrane, and 
become aggregated in groups situated either deep 
in the tissues of the sponge or even in the strands of 
tissue above mentioned.” 
Whether the reproductive cells of the gemmule 
arise from a single cell by proliferation or represent 
an aggregation without a common origin is still 
unsettled, but the latter view is held by most in- 
vestigators. If they do arise from a single cell, as 
H. V. Wilson (1902) admits is a possibility, the 
gemmule formation may be considered a kind of 
