THE 
AMERICAN NATURALIST. 
Vor. xv. — SEPTEMBER, 1881.— No. 9. 
VARIATIONS IN A COPEPOD CRUSTACEAN. 
BY CARL F. GISSLER, PH.D. 
gs March, 1878, a large, deep pond near Glendale, Long Island, 
was found densely populated with blood red Copepod Crusta- 
ceans, which, microscopically examined, proved to be a, form 
slightly aberrant from Diaptomus sanguineus, described by Pro- 
fessor S. A. Forbes, who figured its inferior and superior maxilli- 
ped and fifth pair of legs of the male and female. 
The Long Island form? is unquestionably the same species as 
that from Illinois, but the climate and locality have effected slight 
morphological changes of those organs which in Copepod Crus- 
taceans are most liable to occur. The differences noted between 
the individuals from the two localities are, however, very trifling, 
and its elevation to the rank of a new species would not be advis- 
able. It appears, as in so many other instances, that careful 
€xaminations of a species from different localities do not demon- 
Strate the constancy, but the evolution of the same. The changes 
Sometimes concern insignificant structures, but often also the 
Most important parts used by the systematist in describing a 
Species, 
To make the study of Copepods? in general, better understood 
to the amateur, I have more thoroughly described and figured all 
their external structures. 
The body of Copepoda is more or less distinctly segmented and 
Bulletin of the Illinois Museum of Natural History. No. 1. List of Crusta- 
yink with descriptions of new species, by S. A. Forbes, 1876. 
Measures 3™m. in length. 
_. Consult also « Die freilebenden Copepoden,” by Professor De. GC, Claus. Leip- 
8; 1863, page 200. 
VOL. XV.—No. 1x, 48 
