100 BULLETIN OF THE 
granules observed in the cells are food material is indicated by their 
abundance in cells lying next to the reticulated cells of the calomic 
epithelium (Figs. 6, 28, 56). 
My conclusion, then, is this: Gemmiparous tissue is a rapidly as- 
similating tissue, possessing large nuclei because actively assimilating, and 
staining deeply because full of food material. 
While for Nussbaum, as already quoted (page 71), “indifferent cells” 
are essential to the reproduction of individuals by non-sexual as well as 
by sexual methods, Seeliger (90, p. 596) has concluded that “ die Vor- 
gänge bei der Knospung der Bryozoen uns zeigen, wie histologisch sehr 
bestimmt differenzirte Gewebe einen ganz embryonalen Charakter wie- 
dergewinnen können. Mehr noch als bei der normalen Knospung am 
freien Stockende ist dieses Vermögen bei der Regeneration der Polypide 
der Ektoprokten oder der Köpfchen der Pedicellinen ausgebildet. In 
diesen Fällen schen wir ein plasmaarmes, äusserest feines Plattenepithel, 
das über sich eine mächtige Cuticula ausgeschieden hat, sich in kubische 
und cylindrische plasmareiche Zellen zurückverwandeln und durch eine 
Einstülpung ein neues Polypid bilden, in welchem schliesslich die man- 
nigfachsten Gewebsformen vertreten sind.” 
It seems to me that many facts in the budding of Bryozoa are strongly 
in favor of Nussbaum’s hypothesis, On this assumption, we can best 
understand why in Cristatella there is not an invagination of the ecto- 
derm, and why instead a stolon is formed in the embryo, which passes 
along at the base of the ectoderm and at intervals gives rise to the 
inner layer of the body wall. I believe it is becanse the outer layer 
of the body becomes so rapidly differentiated by the secretion of the 
1 Other observers describe gemmiparous tissue as being either rich in food or 
deeply staining. Seeliger (’85, p. 588) speaks thus of the mesodermal gemmiparous 
tissue in Salpa: “Die einzelnen Zellen sind grossblasig, enthalten einen runden 
Kern und führen Oel- und Fettsubstanzen die als Reservematerial beim Aufbau 
des embryonalen Leibes weiterhin in Verwendung gelangen.” Von Wagner (’90, 
p. 377) says of the indifferent cells which are being transformed into the new 
pharynx of dividing Microstoma : “ Dieselben nehmen an Grösse zu, . . . indem 
gleichzeitig ihre Protoplasmaleiber feinkörnig granulirt und für Farbstoffe imbibi- 
tionsfähiger werden.” 
In some sections of gemmules of Esperella fibrexilis, H. V. Wilson, of which 
Dr. Wilson has very kindly sent me several slides, I find the outer layer of young 
gemmules, in which the inner layer has been newly formed, stained very deeply. 
Observed with a Zeiss Apochr. 4.0 mm., Ocs. 8 and 12, the cell contents are seen to 
be evidently of two kinds, — light and deeply stained. The latter appearance is 
due, in part at least, to small dark granules, which can be discerned without much 
difficulty. 
