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PACIFIC SCIENCE, VoL XX, April 1966 
these were not accurately timed, their rates ap- 
peared to be synchronized. This is much slower 
than the rate of contractility recorded for C. 
sowerbyi frustules by other workers (Crowell 
and Lytle, 1955:255). Furthermore, although 
this process may have something to do with 
locomotion, the contractile waves associated 
with Figure 10 D, E, F, G and H are those of a 
frustule already attached. While certain of these 
contractile waves (Fig. 10E, F, G, H) might 
serve to carry developing nematocysts into the 
forming capitulum, other waves seem to carry 
materials in the opposite direction; thus their 
function remains obscure. Fifteen hours later 
the once horizontal frustule had assumed a 
vertical position and already a capitulum was 
formed. No divisions occurred. 
On October 23, 1963, five atentacular colonies 
were placed in approximately 20 m/c of Zn 65 
diluted with 30 ml of filtered culture water. The 
purpose of this experiment was to follow "hot” 
frustules through several generations in an at- 
tempt to prove that, in mixed cultures, only 
atentacular hydranths would be radioactive. A 
reciprocal experiment was planned for the frus- 
tules of tentacular hydranths. These experiments 
are being repeated, using a Packard Tri-carb 
liquid scintillation counter and weak (low en- 
ergy) Betas In the hope that the possibility 
of knocking out tentacle-forming mechanisms 
might be lessened. 
Figure 11 shows frustule budding and loco- 
motion which occurred on October 30, 1963 in 
three of five radioactive, atentacular hydranths. 
This is included not because it is normal but, 
since the process is exaggerated, because a pos- 
sible method of locomotion is suggested which 
normally cannot be seen. Culture 5 contained a 
large frustule 575 /a long, 100 g, wide at its 
thicker end, and 75 u wide at its thinner end. As 
illustrated, this frustule ( B ) when observed at 
10:20 AM lay some 2 mm removed from the 
hydranth ( A ) from which it budded, yet it was 
still connected by an extremely delicate, but 
nevertheless distinct, "mucus” tube whose diam- 
eter was approximately 50 /a. By 11:00 AM this 
frustule slowly changed from a horizontal to a 
vertical position, only to assume again a hori- 
zontal position with its smaller end pointing 
away from B. By 4:00 PM it had moved to point 
C some 825 /a from B. Here, as at B, it slowly 
righted itself, only to assume again a horizontal 
Fig. 10. Schematized drawing of frustules. A, B, C, and D, Changes in shape due to wave of contractility; 
E, failure of frustule to fragment; and F, G, and H, more than one wave operative. (Numbers correspond to 
ocular micrometer spaces of 25 M and base line under D, E, F, G, and H signify attachment.) 
