ON THE VARIATION OF THE STATOBLASTS OF 
PECTINATELLA MAGNIFICA FROM LAKE 
MICHIGAN, AT CHICAGO. 
C. B. DAVENPORT. 
Tuis study is. concerned with the hooks on the statoblasts 
of one of our common fresh-water Bryozoa — Pectinatella mag- 
nifica Leidy — taken in August, 1898, from the Jackson Park 
lagoon, Chicago, connected with Lake Michigan. 
Pectinatella is a genus comprising two known species: 
Magnifica, found in the United States west of the Rocky 
Mountains, and elsewhere reported only from Hamburg, 
whither it has doubtless been imported ; and Gelatinosa Oka, 
from Japan. The most striking peculiarity of the genus is 
the close association of many colonies, which, by secreting 
together a gelatinous base, come to lie on the surface of a 
great globular gelatinous mass. One is inclined to think at 
first that the whole mass must have been produced by the 
activity of a single colony; but it is certain that it is due to 
the activity of a number of independent but associated colonies. 
The separate colonies are, however, probably all derived from 
a single statoblast, the descendant colony of which has repeat- 
edly divided to produce the colony complex. Consequently, 
all the associated colonies are closely related; this has an 
important bearing on our results. 
The statoblasts are formed inside of the colonies and fre- 
quently in large numbers. In twenty-seven colonies, in which 
all fully formed statoblasts were counted, the maximum num- 
ber obtained was forty-six, the minimum was four; and the 
mode was at twenty to twenty-four. As all colonies contained 
1 A possible third species of this genus has been named by Hyatt (’66~'68) 
Pectinatella Carteri, from a single statoblast described by Carter (59), remark- 
able for its hooks, which grow only at the ends of the statoblast and which are 
furnished with many lateral claws. 
959 
