No. 407.1] THE CREST OF DAPHNIA HYALINA. 887 
is best shown by the accompanying series (Fig. 3), obtained in 
each case from single collections from Pine, Okauchee, and 
Fowler Lakes. It will be observed that in the two former 
every transition exists, from the low, evenly rounded to the 
extremely recurved and elongated crest, 
and the two series are seen to include 
all the American forms described, except- 
ing perhaps the extreme of the triangular 
and the high-rounded types of develop. Wf &» 
ment. 
The amount of these variations was 
not uniformly great in all the lakes 
studied, nor for all the sea- f 
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Fic. 4. — Map showing di i t rn Wisconsin. Taken from U. S. 
Topographical Survey. Lakes Laura and Garvin inserted by writer. 
were made. Thus, several collections taken from Beaver, one 
summer, showed the prevalence of a high-rounded crest with 
slight tendency to antero-dorsal angulation, while the following 
summer many crests exhibited a distinctly recurved apex. 
Lake Garvin, which communicates with Lake Okauchee by 
means of a channel having an approximate width of fifteen 
feet and depth of six feet, nevertheless appears to retain a 
