PROGRESS IliT BIOLOGICAL INQUIRIES, 1927 229 



same number on the established shell beds, but the bags could be 

 stacked so that the yield per square yard of available ground could 

 be increased proportionately to the depth of the water. Whereas the 

 shell beds utilized only two dimensions of space, the bags utilized 

 three dimensions, for they utilize the whole vertical range in which 

 the larvffi will set. In Onset this was found to be from 2 feet below 

 high-water mark to several feet below low-water mark. 



Observations were made on the larvae by making daily tows with a 

 plankton net at various water levels and at all stages of the tide. 

 Daily records w^ere kept of the water temperature and salinity in 

 the neighborhood of the spawning and shell beds, a survey was made 

 of the distribution of salinity over the whole harbor, and the velocity 

 of the tide at all stages of ebb and flood was determined. The re- 

 sults may be summarized as follows : 



1. The water temperature ranged from 65° to 79.5° F., with an 

 average for most of the summer of 75°. 



2. Spawning took place about July 12, and the young straight- 

 hinge larvae were seen July 14. 



3. Larvae were found in the water at all stages of the tide. They 

 were most abundant near the .surface, gradually diminishing in 

 number at the lower water levels, and at the bottom were very few in 

 number or entirely absent. 



4. As the water is being stirred constantly by the action of the 

 tide, and as very little fresh water enters the harbor, the salinity is 

 virtually constant and is the ,same at the bottom as at the surface. 

 The range of salinity was from 25 to 29.65 parts per thousand 

 through July, August, and September, with an average of 26. 

 There was no observed effect of these changes in salinity on the dis- 

 tribution of the larvae. 



5. The first .setting took place on August 1, and setting continued 

 at intervals of a few days until August 19. 



The investigations show that the wire bags are superior to methods 

 commonly used for catching spat and make available ground which 

 at present is not employed for thi.s purpose. 



Three years of experimenting have proved definitely that inshore 

 areas, such as Milford Harbor and Onset, can be developed as oyster- 

 seed producing areas by establishing spawning beds and planting 

 suitable set collectors on the tidal flats. The wire bags filled with 

 shells have proved to be an efficient, cheap, and practical means for 

 collecting oyster set and are suitable for use on a large commercial 

 scale. 



OYSTER DRILL 



The study of the life history and biology of the oyster drill 

 {Urosalpinx cinerea) was carried out by Dr. H. Federighi in the 

 United States Public Health Laboratory at Craney Island, Norfolk, 

 Va. The investigation for the past year included the following: 

 (1) A study of the distribution of the drill in Hampton Road.s; (2) 

 survey of the damage done by it in the region of Hampton Roads; 

 (3) study of the life history of the animal; (4) laboratory and field 

 experiments on its behavior, habits, and feeding; and (5) study of its 

 migrations. 



