ENTOMOSTRACA OF MINNESOTA. 267 
Polyphemus pediculus—Lilljeborg, De Crust. ex ord. trib. 
Polyphemus oculus—Leydig, Naturg. d. Daph. 
Polyphemus pediculus—Schoedler, Neue Beitr. zur Naturg. d. Cladoceren. 
Polyphemus kochii—Schoedler, Neue Beitr. zur Naturg. d. Cladoceren. 
_ Polyphemus oculus—Schoedler, Neue’ Beitr. zur Naturg. d. Cladoceren. 
Polyphemus pediculus—P. E. Mueller, Danmark’s Cladocera. Kurz, Dodekas neuer 
Cladoceren. Weismann, Beitr. zur Naturg. der Daphnoiden. Birge, Notes on 
Cladocera. 
Polyphemus occidentalis—Herrick. 
There are two well-marked varieties of this species: one is found 
commonly in the clear lakes; the other, which I have only once seen, 
was found in a very shallow weedy marsh. The difference in size is 
quite remarkable. Our ordinary form measures less than 1.0 mm. 
The larger form, including the stylets, is 1.6 mm. The ordinary 
variety, although highly colored, is yet transparent, while the large 
variety is deep red and quite opaque. The relationship between the 
two forms is quite like that maintaining between Diaptomus stagnalis 
and D. sanguwineus. Some slight structural differences are observable 
between the two varieties, as in the form of the antennules, yet quite 
insignificant when compared with the striking difference in size and 
coloration. 
The feet of this species have not been fully figured hitherto and are 
accordingly given on Plate LXIX. Some minor differences may be 
noted between these figures and those given by Lund. 
*Polyphemus stagnalis Herrick. 
In order to make the relation clear between these forms, I add 
measurements of this species, following each with the corresponding 
measurement of P. pediculus in parenthesis; animals of the same age, 
as far as possible, being chosen. Head (capsule of eye) 0.3 mm. (0.2 
mm.); head and thorax 0.7 mm. (0.45 mm.); abdomen 0.7 mm. (0.56 
mm.); caudal stylet 0.36 mm. (0.26 mm.); caudal filaments 0.36 mm. 
(0.3 mm.) Whole length of antenne 0.54 mm. (0.42 mm.); first, 
second and third joints of the three-jointed ramus 0.08, 0.06 and 0.10 
mm., respectively. The formation of the resting eggs or ‘‘dauer-ei”’ 
seems to go on at the same time with the parthenogenetic repro- 
duction. 
GENUS BYTHOTREPHES Leydig. 
Much like Polyphemus, but the external appendage of the feet is 
rudimentary, and the abdomen extends out into a most enormous 
spine. The single species is that described by Leydig as B. longimanus, 
which was found in the stomach of Coregonus wartmanni. B. ceder- 
stromit of Schoedler and P. E. Mueller, the latter author now identifies 
