972 The American Naturalist. [November, 
be invoked to accomplish this end in the case under discus- 
sion. 
In passing from below upward in the stem of a plumularian 
examined just before the appearance of the gonangia, we 
find that the sex cells intergrade perfectly with the ordinary 
endodermal cells, many of which are themselves destined to 
become sex cells. The endodermal cells, then, in the distal 
part of the stem, contain that which will ultimately become 
ova or spermatozoa, or they contain what might be called the 
undifferentiated sex elements. A given colony of Aglaophenia 
is always unisexual. That is, all the gonangia contain sex 
cells of one kind, and both ova and spermatozoa are never 
found in one colony. 
Now it is evident that the hooking together of a male and a 
female colony by the upper parts of their stems, accompanied 
by a dissolving of those portions of the perisare which are in 
contact, would leave only the thin ectoderm between the endo- 
dermal cells of the two colonies, and a communication between 
the undifferentiated sex cells would be an easy matter; for Weis- 
mann found that the undifferentiated sex cells exhibited pro- 
nounced amceboid movements’ and such movements would, 
of course, greatly facilitate conjugation. The ameboid cells 
observed by me in the clasping hooks may be of significance 
in this connection. Not only did these cells exhibit activity in 
sending forth pseudopodia, but they also moved bodily from 
place to place among the surrounding cells. 
State University of Iowa, Sept. 26, 1895. 
EXPLANATION OF PLATE. 
en 
. Colony of Plumularia pinnata Linn. showing (a) hydro- 
cladial extensions; (b) forking of ends of hydrocladia ; 
(c) new colony still attached to parent stock ; (d) new col- 
ony separated from parent stock. 
New colony, magnified, showing polyps and rootlets. 
Portion of hydrocladium showing terminal extension. 
Tip of hydrocladial extension showing (a) the budding of 
a new colony. 
` Š This fact was repeatedly observed by the present writer. 
i & bP 
