OR FRESH WATER POLYZOA. 183 
It was firmly imbedded, but when we finally succeeded in 
bringing the under side in view, the rich harvest of speci- 
mens amply rewarded our labors. 
No marine or fresh-water animals of our northern cli- 
mate excel the Pectinatelle in beauty, or equal them in 
the tropical profusion with which they grow. The clus- 
ters, some as large as our heads, others broad and flat, 
were covered by hexagonal figures about an inch in diam- 
eter, traced by the plumed tubes of thousands of Polyzoa. 
Each hexagonal pattern, and there were hundreds in 
Some settlements, was a separate colony, The deep, 
amber-color of the gelatine beneath shone through their 
central spaces, and each thread of the dense fringe sur- 
rounding them was stained with a tiny scarlet dot, the 
mouth of a polypide ; the outline of one of these is given 
in Plate 4. 
The cause of so many being assembled on one common 
deposit of jelly, is not the least curious fact in the history 
of the genus. A minute examination proves that a col- 
ony of Pectinatella is little more than a hollow case, dis- 
tended by the fluids within, which prevent the soft walls 
from collapsing, and support the polypides protruding 
from the upper side in radiating lines. When this hollow 
Dee, or ccencecium, attains the length of an inch, or an 
inch and a half, a crease shows itself as if a cord had been 
drawn tightly about the soft walls. This, deepening, 
finally cuts the colony into two smaller ones, and these, 
h they grow, divide into four, which in turn divide into 
sixteen, and so on. Where this increase is very rapid, 
the interior. colonies are forced to expand upward, and, 
adding to the gelatine as they rise, build up, in some in- 
stances, clusters several feet in diameter, and eight or 
More inches in thickness. 
