308 JULIAN §. HUXLEY 
(2) Suspensions of common sea-water Bacteria killed by 
heating were added daily. 
(3) Masses were put in vessels, together with fresh Ulva, to 
see whether they would ingest the swarm-spores, 
(4) Sterile solutions of Peptone in sea-water, of various 
strength, were prepared. The restitution-bodies were trans- 
ferred to this through four changes of sterilized sea-water, 
the pipette being sterilized between each operation. Although 
somewhat over 50 per cent. of the cultures thus prepared 
became contaminated, yet a number remained free of bacteria. 
In all these, however, the choanocytes underwent regressive 
changes, actually sooner than in normal sea-water, and the 
masses died within a few days. 
(5) ‘Sponge Broth’. 3c... of chopped sponge was 
extracted in 20 ¢.c. of sea-water and sterilized, and restitution- 
bodies transferred to it as under (4), but again with no success. 
(6) Ammonium lactate of 0-1 per cent. concentration 
was prepared and a trace of phosphate added (cf. Peters, 14), 
and then sterilized. Again some. restitution-bodies were 
transferred to the medium without infection, but all contracted 
and died speedily. 
(7) Under gauze, in the circulation (at Wood’s Hole). Unfor- 
tunately these experiments had to be discontinued. ‘The 
restitution-bodies remained healthy for some time, but growth 
could not be detected. The fact that normal regenerates throve 
better and actually grew in these conditions, warrants the 
belief that some modification of this method might be sue- 
cessful. 
Although all methods so far tested have proved unsuccessful, 
yet I feel sure that choanocyte masses could be supplied with 
food. It is possible that experiments in circulation would 
succeed best at Naples, where Sycon establishes itself and grows 
in the tanks. Further, experiments of this nature would most 
profitably be undertaken in the cooler months (see § 1 of this 
paper). At Wood’s Hole I found that covered cultures kept 
cool in the circulation throve better than those exposed to 
air-temperature, 
