280 Evolution of Branchiopod Crustaceans. [ April, 
EVIDENCES OF THE EFFECT OF CHEMICO-PHYSI- 
CAL INFLUENCES IN THE EVOLUTION OF 
BRANCHIOPOD CRUSTACEANS. 
BY CARL F. GISSLER, PH.D. 
URING the winter months Eudbranchipus vernalis Verrill,! 
occurs near Maspeth, L. I, in immense numbers, in large 
communicating ponds containing clear, yellowish, fresh water. 
In January 1880 I found in a small and entirely isolated pool, 
less than a hundred paces from the above-mentioned place, a 
number of perfectly colorless, smaller, but sexually mature indi- 
viduals of these branchiopod Crustaceans. The bottom of the 
pool is a white and very soft clay, and the water itself is of a 
milky color, I collected a number and observed the following 
differences : , 
A. Very few individuals of both sexes bearing, with the excep- 
tion of the transparent body and the red furca of the post-abdomen, 
the same characters as Eubranchipus. 
B. A great number of colorless individuals from fifteen to 
twenty-two mm. in length. These differ from the larger, red 
Eubranchipus, in the following particulars. Cephalic scute large 
and convex; basal joint of male clasper cylindrical; claspers 
crossing each other, short, tip of second joint with a blunt minute 
tooth; second joint more or less conical, tapering. A more full 
account I will soon give in Professor A. S. Packard’s monograph 
on Phyllopod Crustaceans of the sexual organs, copulation and 
the biology of these colorless individuals, 
C. A single specimen of male Chirocephalus. 
D. A hermaphrodite. Sexual organs separate, both male and 
female claspers present? 
E. A single male individual with a minute tooth on the second 
joint of its right clasper; tooth wanting on the left. Left clasper 
in normal position, right clasper twisted around, thus apparently 
preventing the animal from using it in copulation. The tooth is 
probably a substitute for the distorted hook, and assumes its func- 
1« Observations on phyllopod Crustacea of the family of Branchipidz, with de- 
scriptions of some new genera and species.”” By A: E. Verrill, professor of zodl- 
og I 
“ enna this hermaphroditic form in AMERICAN NATURALIST, February, 1881, 
pages 136 to 139. 
