2 BULLETIN OF THE 
tenz, die Theilbarkeit auf geschlechtlichem oder ungeschlechtlichem 
Wege, spontan oder künstlich bedingt, ist an das Vorhandensein undif- 
ferenzirter Zellen gebunden und ist um so grösser, je weiter im Organis- 
mus diese Zellen verbreitet sind”; and, finally, to the idea which is 
implied in the conclusions of Nussbaum (’80, pp. 106-113) and Weis- 
mann, that germplasma does not find its origin in the parent individuals, 
but is merely borne by them in its unbroken passage from generation 
to generation. 
This hypothesis is simply that there is in every stock of Bryozoa a mass 
of indifferent cell material which is derived directly from indifferent cells 
of the larva or embryo, and whose function is to form the organs of the va- 
rious individuals, including the polypides. This indifferent cell material 
lies in the body wall, principally at the growing tip or margin of the 
stock. By its growth and differentiation it gives rise to the body wall, 
muscles, etc., and at intervals it leaves behind, as a portion detacned 
from itself, a mass of indifferent cells, which is capable of forming a polyp- 
ide, or of becoming a new centre of growth, or of both, Which of these 
possibilities will be fulfilled, where and when these masses of indifferent 
cells will be left behind, depends upon the necessities of the species, and 
the variations in these respects give rise to the peculiar characters of 
the different stocks, 
This hypothesis differs from that of Braem in that the pre-existence 
of a Knospenanlage assumed by Braem is, according to my view, a non- 
essential feature in the formation of the colony; the pre-existence of an 
indifferent cell mass, which does not itself constitute buds, but may give 
rise to masses which can, is the only essential feature. 
As a first application of this hypothesis I refer the reader to the con- 
ditions of stock formation in Paludicella, already described. We find at 
the tip of the colony a mass of large proliferating cells, which I regard 
as histologically undifferentiated. These cells give rise to the body wall, 
— the cystid, — and at intervals leave behind three masses of cells, which 
I regard, from the fact that they retain their cuboid condition, as well 
as from their ultimate fate, as indifferent or embryonic. The median 
mass of each of these gives rise to a polypide, and to one only. The 
lateral masses form centres of growth similar to the one from which they 
were derived. 
In order to reproduce the arrangement of individuals in the stock re- 
sulting from this manner of budding, we may make use of some graphic 
method of representation, as Smitt (765%, pp. 139, 140) did long ago, and 
as Allman (70), Semper (’77, pp. 67-78), Chun (’88, pp. 1167-1180), 
