228 Herbert W. Rand 
deeper recession of the entoderm and a thicker covering of ecto- 
derm than at thecorresponding proximal cutend. ‘These Aiptasia 
tentacles, when cut, contracted to such an extent that their cavities 
were nearly or quite obliterated. Therefore neither proximal nor 
distal cut ends were actually open in the sense that they were in 
Condylactis. 
In connection with this study of fragments of tentacles of Aip- 
tasia, I was interested in repeating the observation made by 
Parker (’96) upon Metridium. He found that an excised ten- 
tacle “has a strong resemblance to an independent organism, 
and by means of its cilia glides slowly through the water with its 
base forward, a fact in accordance with the observation that on 
attached tentacles the current produced by the cilia moves from 
base to tip” (p. 110). Fragments of Aiptasia tentacles remained 
alive for seven or eight days moving about slowly and continuously 
with proximal end foremost, and showing occasional spontaneous 
contractions. Many of the fragments were slightly curved and 
therefore moved in circles. The cut ends appeared closed but it 
1s probable that the proximal end, at least, was not perfectly closed 
for, beginning usually a day or two after the cutting, there were 
occasional discharges, through the proximal end, of substance 
from the interior of the tentacle. ‘This substance consisted chiefly 
of the brown Zooxanthellz, to which the tentacle owes its color. 
Sometimes these bodies were discharged in a continuous stream 
for several minutes, as if by the action of the entodermal cilia. 
As a result of these discharges the fragment faded in color and 
diminished in size. By the third or fourth day the fragment had 
become quite colorless and was reduced to a half or even to a 
fourth its original size. Some of the later discharges were of 
colorless material. ‘This was probably disintegrated entoderm, 
yet the ectoderm was perfectly intact and its cilia continued to 
beat vigorously until within a few hours of the final disintegration 
of the fragment. ‘The fragments of tentacles of Condylactis did 
not move about, doubtless owing to their relatively greater bulk. 
They disintegrated sooner than fragments of Aiptasia, probably 
because of the wide open proximal end. 
In looking for these expressions of polarity, it occurred to me 
