88 
JTatiord History Society of JSf. Bulletin No. IV. 
streams, and is filled by the tide twice each day through four narrow 
channels. The degree of hardness of the surrounding rocks is very 
favorable to the existence of a great variety of life, for they consist 
largely of soft, easily eroded conglomerates and sandstones, which are 
carried away by the strong tides and dejiosited among the islands, 
forming pebble, sand, and mnd bottoms, while numerous trap dykes 
afford rugged reefs and ledges. 
In order to obtain specimens for study two methods are adopted, 
that of searching the tide pools and of dredging. As the tide ebbs 
it leaves pools among the rocks from which the water never entirely 
runs out, but leaves enough for the support of the animal life therein 
until the next flood tide refills it. Wading into these and turning 
over flat stones, pushing aside the great matted masses of seaweed, 
or peering into little hollows and caves in the ledges, the observer 
can study the living specimens in a way that is not possible when 
they are roughly dredged from the bottom. But very many species 
inhabit considerable depths, and then the dredge or trawl must be 
used. A few words as to the method adopted in dredging may not 
be out of place here. 
The instrument used consists of an iron framework two feet long 
and six inches broad, made in such a form that a broad scraping sur- 
face always rests on the bottom, while behind there drags a fine net 
which catches everything that the scraper loosens. The boat being 
brought up into the wind until there is little headway, the dredge is 
let go until it rests on the bottom. Then the sail is allowed to fill 
and rope is allowed to run out to the length of between twice and 
thrice the depth of the water, its amount depending largely upon 
the character of the bottom. If the latter be muddy, just enough 
rope must be used to allow the dredge to just scrape the surface or 
go to a slight depth, for if too much is given out the iron jaws sink 
deep into the mud and act as an anchor. In such a case the rope 
must be allowed to run out freely while the boat is brought around 
upon the opposite tack, and it is lifted as an anchor would be. If, 
however, the bottom be sandy or pebbly less care is required, and 
the dredger soon comes to know the character of the bottom by the 
feeling of the rope and can regulate its amount accordingly. 
In considering the Zoology of the Invertebrates of the Bay, I 
have deemed it best to endeavor to present to you an idea of its 
general character, together with some observations upon the habits 
