208 ARTHROPODA [CH. 



The Phyllopoda are divided by Dr Caiman, our best authority, 

 into four sub-orders, viz. : 



Sub-order 1. Anostraca. 



Long-bodied Phyllopoda devoid of a brood-pouch and of 

 carapace, the second antennae are not used as swimming organs 

 but are converted into curious claspers by which the male 

 grasps the female. Ex. Artemia, Branchipus. 



Sub-order 2. Notostraca. 



Long-bodied Phyllopoda with a broad flattened carapace. 

 Antennules and antennae vestigial. Ex. Apus. 



Sub-order 3. Conehostraca. 



Phyllopoda with a bivalve carapace. Body of moderate 

 length, antennae forked and used for swimming. 



Sub-order 4. Cladocera. 



Phyllopoda similar to the Conehostraca but with still 

 shorter bodies using the space between carapace and body as a 

 brood-pouch. Ex. Simocephalus, Daphnia. 



The Anostraca, Notostraca, and Conehostraca Jive in fresh water 

 and as a rule in the standing water of pools and ponds ; they are more 

 rarely found in brackish or salt water. They swim actively about by 

 means of the vibrations of their flattened limbs. As a rule aquatic 

 animals swim with the upper surface towards the surface of the water, 

 but the Phyllopoda seem very indifferent to this rule, and are quite 

 frequently seen swimming upside down. The Cladocera almost always 

 swim upside down, the genus Daphnia however usually adopts a 

 vertical position with the head uppermost. These last are much the 

 most widely distributed group of the Phyllopoda. There are not 

 only fresh-water but also many marine species. The latter occur in 

 great swarms in many parts of the ocean. 



Order II. Ostracoda. 



This order (Gr. oorTpaKwSr/g, shell-like) contains a great number 

 of species which do not differ greatly from one another in outward 

 appearance. In form they resemble Dapknia, but the head does not 

 protrude from between the valves of the carapace, and some of the 

 internal organs of the body, viz., the ovary or testis and branches of 

 the liver, are prolonged into the valves of the carapace. This latter 

 is a very characteristic structure, consisting, like the shell of the 



