NOTES UPON CORDYLOPHORA LACUSTRIS 



CHAS. W. HARGITT. 



VARIABILITY among living things, whether in habits, struc- 

 ture, or development, is now so fully recognized as to need no 

 special emphasis as an important law of nature. The list of 

 facts is not, however, so complete as to render others unim- 

 portant ; and it is with this point in view that the following 

 notes have been thought worthy of record. 



Cordylophora as a genus of hydroids has long been of more 

 than usual interest to the biologist as affording among its 

 phylum a rather striking illustration of remarkable range of 

 environmental adaptation. Its ability to range from a dis- 

 tinctively marine habitat to that of fresh water has long been 

 known, and is well expressed in the specific name applied to it. 

 Allman was, I think, the first to call particular attention to 

 this peculiarity and to make some experiments and repeated 

 observations of very interesting nature in connection with it. 1 

 It is with a view to confirming and extending these observa- 

 tions that attention is directed to them in this connection. 



Through the kindness of Mr. H. W. Britcher, of Johns 

 Hopkins University, I received in December, 1895, a colony of 

 these hydroids obtained from near Baltimore, Md. They had 

 been collected by Mr. Britcher some time earlier and were 

 brought to Syracuse in about a pint of brackish water, attached 

 to a bit of slag upon which they grew, and upon which were 

 also growing several specimens of acorn barnacles, Balanus, 

 and bits of a filamentous marine alga. They remained in my 

 laboratory for several weeks, where they were inspected by 

 students and visitors. Twice during this time they were 

 frozen almost solid and, as I supposed, killed by the ordeal. 

 They were therefore set aside and for several weeks unob- 

 served. A subsequent examination, however, showed a few 



1 Allman, Gymnoblastic Hydroids, p. 253. 



