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DEPARTMENT OF MARINE BIOLOGY. 219 



Thus natural sea-water dissolves CaCOs and appears to lose a certain amount 

 of CO2 in the process, but we hesitate to assert that this action is due to free 

 CO2 in the sea-water. 



If there is free CO2 in sea-water, dissociation of H2O in the sea-water must be 

 quite different from that of pure water. 



The theoretical considerations, together with quantitative data, for which 

 this report affords no space, will be published later. 



Further Studies on CO2 Production in the Medusa Cassiopea. 



A new and rapid method was devised to estimate amounts of CO2 produced 

 in sea-water by marine animals. I extended the previous study of small circu- 

 lar pieces of the animal to the half or the whole animal. Very extended quan- 

 titative data were collected on the metabolism under the following conditions: 



1. Effect of contraction (resting and contracting). 



2. Effect of light on both resting and contracting medusa. 



3. Size and metabolism. 



4. Under different concentrations of sea-water {electrolytes). 



5. Effect of temperature (not complete). 



6. Effect of sense-organs (with Dr. Gary). 



The general conclusions are exactly the same as those of last year, but the 

 averages for the production of CO2 under these different conditions have yet ta 

 be calculated, and until this has been done we can not present a report. 



Report on Systematic Study of the Leodicidce in 1915, 

 by A. L. Treadwell. 



My work in 1915 was a continuation of that of previous years on a system- 

 atic study of the Leodicidse. In Porto Rico, no representatives of this family 

 were found in Guanica Harbor, but Leodice fucata (the palolo) and Niddion 

 kinbergii occur in the coral rock off the entrance to the harbor, and L. rubra 

 is abundant in the channel at its entrance. These are all common forms at thfr 

 Tortugas. A Leodice and a Marphysa, both probably new species, were col- 

 lected in coral rock near Guanica Lighthouse. 



In Condado Bay, near San Juan, I collected a few Marphysa fragilis, which 

 was previously known only from a very limited locaHty at Loggerhead Key 

 in the Tortugas; and a small Lysidice was found in the hard rock on the sea- 

 ward side of the shore of the bay. Other annelids, especially capitellids, 

 Clymenella, and Chcetopterus, are numerous in Condado Bay, but no attempt 

 was made to collect them. 



In Florida, collections were made in Key West Harbor, at Boca Grande and 

 Marquesas Keys, and at the Tortugas. In the former localities, species of Mar- 

 physa and of lumbrinereids were most abundant, while at the Tortugas, 

 Leodice is the most common genus. In my report for 1914, I said there are 

 no mud flats in this locality; this proves to have been erroneous, as mud flats 

 have formed at Long Key since the great hurricane of October 1910, and 

 Onuphis and lumbrinereids occur there. Some species not previously seen 

 in the Tortugas were dredged at various places in the channels and off the south 

 shore of Loggerhead Key. These are mostly very small forms, living in 

 crevices in the loose, broken coral rock. About 90 drawings have been made 

 of the species collected this year, and it is probable that practically all of the 

 shallow-water Leodicidse occurring in the Tortugas have now been described 

 and figured. 



According to previous records, the swarming of palolo should have occurred- 

 this year between June 30 and July 6, for the moon's last quarter fell on July 3.. 



