12 



antenne of the second pair ; 0, the maxillary part ; 0, 

 the mandibular leg, four jointed ; M, muscular band, 

 fastened to the inside of the shields ; the other organs 

 are like those of the fully developed Cypris. {Fig. TV, 

 plate I.) The shields of Cypris become very transparent 

 when touched with a drop of solution of caustic potassa. 

 The male Cypris is very seldom observed, and the eggs 

 are produced by the females as it is the case with Dap li- 

 ma, Sida, the plant-lice, (Aphidse), etc., by partheno- 

 genetical production.* 



The third crustacean occurring in this water, and also 

 the largest, Daphnia pulex (1,2 to 2,2 Mm. long, and 

 0,06 to 1,0 wide) of the order Cladocera or Phyllopoda, 

 is reddish-grey with two scales. The much larger female 

 carries her eggs under the scales on the back, until the 

 embryos are in a forward state of development^ Seen 

 under the microscope, they show a brain, a movable eye? 

 surrounded with crystal-like, globular bodies, a mouth, 

 simple intestine, anus, liver, heart, breathing apparatus, 

 branched antennes, and so forth. The males only appear 

 periodically in the autumnal months ; during the inter- 



plate X, 48 and 49. This species was found by Dr. Budd, in the neighbor- 

 hood of Lake Champlain. Yet two other species are described by J. De Kay, 

 C. agilis and C. simplex from the Lancaster County, Pennsylvania. 



* Their relationship to the Poecilopoda, (Xiphosura) which are represented 

 by the Limulus polyphemus (Horse-shoe) on the eastern coast of N. Amer- 

 ica, is very close. Van der Hoeven says in his work, page 37 (Recherches sur 

 l'anatomie des Limules, Leyde 1838). " Mais soit qu'on range les Limules 

 parmi les Crustac6s, soit qu'on les mette avec les Arachnides, i]s devront tou. 

 jours former a eux seuls un ordre distinct, qui dans l'etat actuel de nos con- 

 naissaDces, est eloigne de tous les autres ordres de ces deux classes. C'est 

 en efet bien gratuitement et seulement d'apres une simple ressemblance 

 exterieure, que la plupart des naturalistes ont place le genre Apus a cdte des 

 Limules. Leur (Phyllopoda) systeme nerveux differe essentiellement de celu 

 des Limules et consiste en deux series de nombreux ganglions. 



f The family Cyproidea is described in James D. Dana's Crustacean-work 

 (U. S. Expl. Exped.,) pp. 1277 to 1304. 



