366 WILSON. MonsIx. 
however, has not been confirmed by later investigators. On 
the contrary Seeliger finds that the bud is not derived from a 
single cell, but is formed in a very different way. According 
to Seeliger (30, 31) the bud, both in Loxosoma and Pedicellina, 
is formed as a papilla of the body wall (or stolon, in the case 
of Pedicellina), an invagination at the end of the papilla giving 
rise to the atrium and alimentary tract. The mesoderm of the 
bud is derived from the mesoderm of the parent, the ectoderm 
of the bud is derived from the ectoderm of the parent; and the 
only new formation is the entoderm, which is produced by an 
invagination of the adult ectoderm, Seeliger’s account destroys 
the possibility of drawing a parallel between sponge gemmules, 
which develop germ layers, and the buds of Loxosoma. 
The internal buds or gemmules of the fresh-water sponges 
have been known since the time of Linnzeus, but their precise 
origin is still open to discussion. 
The ripe gemmule consists of a solid mass of polygonal 
cells, full of yolk, surrounded by a complex capsule. The 
capsule is perforated by an opening (hilum), through which 
in the spring the cellular mass creeps out, developing into a 
new sponge. The capsule is composed of an inner and outer 
cuticular layer, between which is a layer containing skeletal 
elements (amphidisks or other spicules). According to Gotte 
(6), all the cells in a particular region of the body of the 
parent sponge, not only those of the mesoderm, but those of 
the flagellated chambers and canals as well, become trans- 
formed into a mass of yolk-containing cells, which constitutes 
the gemmule. According to Marshall (19), however, the gem- 
mule is formed exclusively from an aggregation of mesoderm 
cells. In whichever way formed, the young gemmule becomes 
differentiated into two layers, an inner mass of larger cells full 
of yolk, and a peripheral layer of cells (Gotte). According to 
Gotte, the peripheral layer of cells secretes the inner and 
outer cuticle, and gives rise to the amphidisks. According to 
Wierzejski (cited from Vosmaer 33, p. 429), the peripheral layer 
assumes the character of a columnar epithelium. Between it 
and the central mass appears the inner cuticular layer. The 
spicules and amphidisks are formed entirely outside the gem- 
