62 REPORT OF NEW JERSEY STATE MUSEUM. 



This grenus is the miost conspicuous, and the one frequently 

 seen. Young hatched with a pendant appendage attached to 

 upper posterior angle of shell, and this soon becoming the rigid 

 spine characteristic of the younger stages and males of the 

 genus. Females almost immediately after birth begin produc- 

 tion Oif egg& by an asexual process. Groups of epithelial cells 

 containing four each are formed and one of the cells of each 

 group develops at the expense of the others, forming the egg. 

 Many such eggs are laid simultaneously and deposited in the cav- 

 ity between the shell and the dorsal part of the animal. 



Daphne pulex (Linnaeus). 



Plate 9. 

 Daphnia. Red Daphv.ia. 



Monocuhis piilcx Linnseus, Syst. Nat., Ed. 10, 1758, p. 634. "In aquis diilci- 

 bus" (Europe). 



Daphnia reticulata (nee Monocuhis reticidatus Jurine) Haldeman, Proc. 

 Acad. Nat. Sci. Phila.. 1843, p. 196. A little pond on the Susquehanna 

 above Columbia, Pa. 



— Underwood, Bull. III. Lab. N. Hist.. IL Oct. 1886. p. 342. Pennsyl- 

 vania. 



Description. — Body stout, thick, usually large. Shell thin, 

 transparent, nearly broadly ellipsoid in contour, and ending 

 superiorly behind in a slender attenuated spine, this often about 

 one-fourth rest length of body. Edges of spine and of shell 

 adjacent with fine small spinules. Head depressed, broad, not 

 crested, and protuberant in front, ventral edge deeply concave. 

 Beak on head below rather attenuated and curved back a little. 

 Fornix high. Eye high, small. Antennules short, conic, reach 

 but little beyond beak. Antennae slender, short. In mature 

 females shell not separated from head by a depression. Pigment 

 spot present. Caeca present, dorsal in position on abdomen be- 

 hind. Abdominal processes approximate, first twice length oi 

 second and third small. Post-abdomen long, somewhat tapering 

 towards end, where rounded. About a dozen subequal post- 

 abdominal teeth, curved, forming two combs. Color transparent 

 to pink or dull red. Length 2.15 mm. 



