Craspedacusta sowerbyi and Calpasoma dactyloptera — Matthews 
247 
6.5 for new cultures to 8.5 for old, well- 
established cultures, with the mean at 7.5. 
The number of hydranths per culture was 
restricted by removal of frustules of 10 atentacu- 
lar and 10 tentacular hydranths. 
Cultures remained covered except when hy- 
dranths were observed or when an oligochaete 
(Aeolosoma hemprichi) and turbellarians (Pla- 
naria sp. and Stenostomum tenuicaudatum ) were 
introduced (Nuttycombe and Waters, 1938) . 
These were directed by "minuten Nadeln” to 
make contact with a capitulum. Then, unlike 
small nematodes whose snake-like movements 
stopped as if the animal had been electrocuted 
(Matthews, 1963:20), Planaria continued to 
struggle even after its twisted, contorted body 
was completely ingested. Because a small worm 
usually filled a single hydranth’s enteron, its con- 
striction allowed the severed "posteriors” of 
large Aeolosoma and Stenostomum to gyrate 
blindly. 
In colonies, unfed hydranths remained "hun- 
gry” even after ingested contents of fed hy- 
dranths cleared and presumably could have been 
freely shared. If clearing denoted digestion, it is 
interesting that it began just below the mouth 
and proceeded toward the attached basal por- 
tion. This was observed in a two-hydranth col- 
ony starved for three days and then fed Planaria 
whose pharyngeal region was gorged with car- 
men. Contact with one of the capitula was made 
at 7:50 AM. By 8:00 AM ingestion was com- 
plete and already the portion nearest the hy- 
dranth’s mouth was beginning to clear. By 8:10 
AM movement down the enteron had progressed 
halfway and, although the end nearest the hy- 
dranth’s mouth was clear, the end farthest re- 
moved was only beginning to be so. By 8: 30 AM 
the mass of carmen particles and the remains of 
the worm entered the base of the unfed hy- 
dranth, and by 10:00 AM had ascended one- 
third its column. The position of the mass as 
such did not further change. However, with 
digestion apparently completed, diffuse, minute 
red granules indicated that phagocytosis had also 
occurred. 
This experiment was repeated the following 
day on the same colony. Once again ingestion 
required only 10 minutes and, as before, diges- 
tion seemed most pronounced in the region im- 
mediately below the hydranth’s mouth. Again, 
in 1/2 hr the almost completely digested mass 
reached the base of the hydranth but, instead of 
entering the base of the other hydranth, it 
ascended the column just descended. And, al- 
though ascending the first half required almost 
2 hr, ascending the last half, plus complete eges- 
tion, required only 10 minutes. As before, small 
red granules remained, indicating that some 
phagocytosis had taken place. Whether or not 
sharing occurred, the unfed hydranth instantly 
accepted a new worm whereas the fed hydranth 
repeatedly rejected it. This, however, may have 
been more the result of unspent nematocysts in 
the unfed hydranth and of spent nematocysts in 
the fed hydranth than the result of hunger per se. 
Discussion pertaining to feeding tentacular 
hydranths is postponed until later. 
Figures 1-4 are drawings of atentacular hy- 
dranths from which detritus and algae ( Tribo - 
0 • 3 m m 
Fig. 1. Craspedacusta sowerbyi. a, d, Two atentac- 
ular hydranths; b, developing bud; and c, centrally 
located attachment point. 
