BRANCHIOPODA. PHYLLOPODA. 375 



A few Cladocera live in the sea, but the greater number of 

 Branchiopods inhabit bodies of freshwater where there is little 

 or no current. Some of them are found in brine pools. 



Sub-Order 1. PHYLLOPODA.* 



Branchiopoda, with dearly segmented body, often enclosed in a ftat 

 shield-shaped or laterally compressed bivalve shell, with from ten 

 to thirty or more pairs of foliaceous swimming feet bearing saccular 

 epipodites. 



The alimentary canal is provided with two lateral hepatic 

 appendages which are as a rule branched and racemose and only 

 exceptionally short and simple. The heart is a long dorsal vessel 

 with numerous paired lateral slits which may extend along the 

 whole length of the body (Fig. 247). The genital organs which 

 are always paired are placed by the side of the alimentary canal 

 and open at the boundary between the thorax and abdomen, 

 a limit which may or may not be marked by other structural 

 features. In the Branchipodidae they are simple, but in Apus 

 they are racemose glands in both sexes. In the females the 

 genital openings are small slits ; in the males of the Anostraca 

 there are protrusible copulatory organs at the openings. 



The males may be distinguished from the females in the 

 Conchostraca by the fact that the anterior or two anterior pairs 

 of legs are armed with hooks, and in the Anostraca by the large 

 size of the posterior antennae, which in Branchipus and Branchi- 

 necta are moreover beset with peculiar appendages. In Apus 

 they are distinguished by the absence from the llth pair of 

 appendages, of the brood pouch, to be referred to directly. 

 The eggs are generally protected during development, being 

 carried about the body of the mother either in a projecting 

 uterine dilatation of the united oviducts, at the base of the 

 abdomen (Branchipodidae), which, unlike the egg-sack, of the 

 Copepoda, is a cellular structure opening by muscular lips ; or 

 between the valves of the shell attached to filiform processes 



* Schaffer, Der Krebsartiger Kief er fuss etc., Regensburg, 1856. A. 

 Kozubowski, Ueber den maiinlichen Apus cancriformis, Arch, filr Natur- 

 gesch., Bd. 23, 1857. C. Claus, Zur Kenntniss des Baues und der 

 Entwickelung von Branchipus und Apus etc., Gottingen, 1873. The 

 same, Untersuchungen liber die Organisation und Entwickelung von 

 Branchipus und Artemia, Arbeiten aus dem zool. Institute, Wien., Bd. 6, 

 1886. A. S. Packard, A monograph of North American Phyllopod Crus- 

 tacea, Washington, 1883. 



