26 BULLETIN OF THE 
sional nuclei. These are the tubular cells already referred to. Some of 
them contain the agglutinated cilia characteristic of flame cells, and they 
arise from large cells, which must indicate the beginnings of the excretory 
tubules of the stalk already mentioned. 
What is the meaning of the fact that no younger stages than these 
occur, although such and all older stages are abundant? Have these 
young stocks been derived from fertilized eggs, or have they some other 
origin ? 
I have already referred to the fact that the great mass of the buds of 
any Urnatella stock are found at the upper end of the parent stalk. The 
lower and middle parts of the stalk possess few buds, although they once 
constituted the upper end of the stalk. What has become of the buds 
which have been lost? Leidy asked this question, and the facts led him 
“to suspect that the branches are spontaneously and habitually detached 
from the parent stem, to become elsewhere attached, and thus form new 
colonies.” I have evidence that raises the suspicion of Leidy to as near 
certainty as can be obtained by use of the morphological method. The 
“‘ youngest stocks” are derwwed from the stolons of the parent stalk, which 
habitually become free for the purpose of founding new stocks. 
To establish this proposition it will be necessary to show, (1) identity 
of structure between old lateral buds and young stocks, and (2) the 
scar of attachment of the young stock to the parent stalk (cf. Plate VI. 
Fig. 58). Of identity of structure there can be no question. Often it 
would have been quite impossible to distinguish between young stocks 
and “stolons” which had been violently broken off from the parent 
stalk and were lying loose in the bottle, were it not for a single criterion, 
namely, the young stocks had dirt adhering to their lower surface. An 
application of the second criterion leads to the same positive result. In 
series of thin sections of young stocks one can always find at one side 
of the median plane the scar of former attachment, which appears as a 
thickening of the cuticula into which ectodermal cells may sometimes be 
seen penetrating (Plate V. Fig. 47). We have here, then, a method of 
non-sexual propagation quite similar to that obtaining in Loxosoma, where 
the buds habitually drop off, so that this genus is commonly said not to 
be stock-producing. This resemblance must be regarded as being purely 
a physiological one, and not in the least implying any closer relation- 
ship of the two genera. 
I have already expressed my belief that the stolons are thrown off reg- 
ularly for the purpose of founding new stocks. On this assumption we 
can account for the rapid growth of the embryonic tissue giving rise to a 
