966 ; The American Naturalist. [November, 
NOTES ON THE REPRODUCTION OF PLUMULARIAN 
HYDROIDS. 
By ©. C. Nurtina. 
During the past spring and summer, while studying the 
Plumulariide at Plymouth, England and Naples, Italy, the 
writer came across certain facts which are deemed to be of 
such general biological importance as to render an immediate 
announcement desirable, without waiting for the completion 
of a work in which a more formal discussion of these facts and 
their significance will appear. 
Asexual reproduction of Plumularia pinnata Linn. 
This species is the most abundant plumularian at Plymouth 
affording ample material for satisfactory study. The first spec- 
imens with young gonangia were brought to the laboratory on 
May 2nd. Ten days before this I noticed that several fresh 
specimens were peculiar in having a number of the hydrocla- 
dia greatly produced into thread-like extensions ending in a 
clavate enlargement. Neither hydranths nor nematophores 
grew upon these processes, although the usual number were 
found in their normal position on the unmodified portions of 
the hydrocladia. 
These specimens were kept alive in a separate jar, and three 
days later it was found that the curiously lengthened hydro- 
cladia had continued their abnormal growth, and that some of 
the enlarged ends had become forked. A microscopic exami- 
nation showed that the hydrocladial extensions were almost 
or entirely destitute of nodes, the whole structure being a sim- 
ple tube, with perisarc, ectoderm and endoderm enclosing the 
axial cavity in which the life currents were moving in un- 
usual activity. The most notable histological feature was the 
surprising number of nematocysts embedded in the ccenosare. 
The colony seemed in good condition, the hydranths being 
fully expanded and active. 
