68 FRANK SMITH. 



In size, mode of branching, number of gonophores and of 

 embryos in the gonophores the colonies are similar to those of 

 C. lacustris, when found in strictly fresh water, as described by 

 Pauly ^ and others. The main stems are but 1-1.5 cm. in height,, 

 but sparsley branched and the branches commonly bear but one 

 gonophore which has usually not more than five or six embryos. 

 Gonophores were present in. July but not in October. 



As opportunity has permitted, other places about Havana have 

 been examined for hydroids, but thus far without success. 



On August 4, during a brief visit to the Illinois River bottom- 

 lands and lakes near Hennepin, I noticed on a partially submerged 

 concrete wall extensive areas bearing organisms that seemed to 

 be hydroid colonies similar to those found at Havana. As there 

 was no time nor equipment for examination of the living material 

 nor for its proper preservation, there is nothing at hand to serve 

 as a basis for the identification of this form except the macerated 

 remains of a few colonies which wer-e scraped off and kept in a 

 vial of water. The skeletal remains of the colonies are indistin- 

 guishable from those of the Havana species and I feel quite sure 

 that the forms are identical and that the species is well established 

 at two places in the Illinois River nearly a hundred miles apart. 



How long this hydroid has been represented in the Illinois 

 River is problematical, but to the writer it seems somewhat im- 

 probable that it was in the Havana region before the opening of 

 the Chicago Drainage Canal, as for several years prior to 1900 

 various observers connected with the Biological Station searching 

 persistently for all kinds of animal life found no such hydroid 

 forms. There is at least a possibility that this hydroid may be 

 found about the docks in the Chicago region where it may have 

 been introduced by vessels from the Atlantic coast and then sub- 

 sequently have been carried through the drainage canal into the 

 Illinois River. More extended observations on its distributioa 

 in the Mississippi Valley are highly desirable. 



University of Illinois, 

 November, 13, 1909. 



^ Zoologiscker Anzeiger, Vol. XXIII., pp. 546-551. 



