ENTOMOSTRACA OF MINNESOTA. 267 



Polyphemus pediculus — LiDjeborg, 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, Daumark'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 foi^ud 

 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 t he 

 two forms is quite like that maintaining between Diaptomns stagnuUs 

 and B. sanguineus. 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. 



*Polyi>ljenius 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 antennae 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. longimanns, 

 which was found in the stomach of Coregonus wartmaniii. B. ceder- 

 stroma of Schoedler and P. E. Mueller, the latter author now identifies 



