PIIYLOGENY OF THE PELECYPODA. 285 



The water of the bay is remarkably clear and pure. It is warmed by the Gulf Stream, 

 and also by rising tides which flow over great areas of sun-heated flats. The water is 

 freshened by Monument River, and by broolis and percolating water entering the bay 

 from the low, gravelly shores. 



The site chosen for operations is alow-lying neck of land in the township of East Ware- 

 ham. At this locality a sand bar is formed by the tide as it rises and flows on the one side 

 to Onset and on the other to Bnttei-milk Bay. The force of the current is very great 

 and it is a noted spot amongst the fishermen for a "set" or "fall" of oyster spat. On the 

 north side of the neck of land a small sinuosity in the shore line forms an almost en- 

 closed pond which is bare at low tide. The greater part of the young Pelecypoda stud- 

 ied, were obtained on the bar and in this pond. For the use of a tempoi-ary laboratory, 

 the bar and the pond, I am indebted to Dr. E. B. Larchar. I am also indebted to him 

 for occasional assistance in prosecuting my work. 



In studying forms of animal life that become fixed to foreign bodies during their early 

 stages of development, it is an advantage if they can be induced to attach themselves to 

 transparent media, such as glass or mica, so that they may be studied by transmitted 

 light without disturbance under the microscope. 



Several attempts have been made by Ryder (62), Horst and Winslow, but with only very 

 partial success, to secure oysters on glass. As I was anxious, if possible, to get oysters 

 growing on glass, in 1887 I tried several methods to accom|)lish the desii-ed end, which 

 were described in my papei- on "Catching Fixed Forms of Animal Life on Transparent 

 IVIedia for Study." The following method was tried and found successful. On the 1.5th 

 of July, 1887, at the suggestion of Dr. Larchar, eai'thenware drain-pipes were partially 

 sunk on the sand bar in an upright position, and loosely filled with broken glass. Six- 

 inch and four-inch pipes were used, and at different elevations above the sand. I did 

 not secure any spat in the four-inch pipes. A six-inch pipe sunk nearly to the level of 

 the bar was successful, but in an unlucky day was filled with sand, and the young oys- 

 ters buried. Six-inch pipes, reaching about ten inches above the bar, were perfectly suc- 

 cessful, and on the glass in them I got large numbers of young oysters. During the 

 summer of 1888 the attempt to get oysters on glass was repeated. On the 18th of July, 

 four six-inch drain pipes were sunk perpendicularly on the bar at the lowest point avail- 

 able at low tide. They stood about fifteen inches above the sand. The last of July, 

 four eight-inch pipes were sunk in a similar position, all were filled loosely with broken 

 glass, and met with entire success. The eight-inch ])ipes wei-e preferred to other sizes 

 as lai'ge pieces of glass could be put in them and the spaces between contiguous plates 

 could be more easily maintained. Long strips of glass, two to four inches wide, the 

 trimmings of glaziers, were used. They were arranged ]ierpendicularly in the pipes, and 

 were readily taken out, examined and cleaned. They were cut as required by one of 

 the rotary, hard steel wheels sold by hardware dealers for that pui-pose. This size of 

 pipe and glass gave such satisfaction that I should use it in future if occasion demanded 

 to the exclusion of other methods that were tried. Suitable conditions for the success 

 of the undertaking were therefore as follows: (1) a strong tide-way, which would bring 

 l)lenty of free-swimming fry, and afterwards abundant food for their maintenance; (2) 



ME5IOIR8 IIOSI'ON SOC. NAT. HIST., VOL IV. 39 



