ENTOMOSTRACA, 



299 



First Sub-Class. ENTOMOSTRACA 



Order I. Phyllopoda. In these at least four pairs of leaf- like swimming 

 feet bear respiratory plates. The body is generally well segmented, 

 and is protected by a shield-like or bivalve shell. The mandibles 

 are without palps, and the maxillae are rudimentary. 

 (a) Branchiopoda. The body has numerous segments and (10-20 

 or more) foliaceous append- 

 ages with respiratory plates. 

 The shell is rarely absent, 

 usually shield like or bi- 

 valved. The heart is a long 

 dorsal vessel with numerous 

 openings. The eggs are able 

 to survive prolonged desicca- 

 tion in the mud. 



BranchipuS) a 'beautifully 

 coloured fresh - water 

 form, with hardly any 

 shell. 



Artemia. Brine - shrimps. 

 Periodically partheno- 

 genetic. By gradually 

 changing the salinity 

 of the water, Schmanke- 

 witsch was able, in the 

 course of several gen- 

 erations, to modify A. 

 salina into A. mil- 

 hausenii) and vice versa. 

 Artemia fertilis is one 

 of the four animals 

 known to occur in the 

 dense waters of Salt 

 Lake. 



ApuS) an archaic fresh- 

 water form with a large 

 dorsal shield. 



Apus is over an inch in length, a giant among Entomostraca. It has 

 an almost world-wide distribution. The appendages are very 

 numerous and mostly leaf-like. They may be regarded as 

 representing a primitive type of Crustacean limb. Professor 

 Ray Lankester enumerates them as follows : 



1. Antenna. 



2. Second antenna. (This is sometimes absent, and 



apparently always in certain species. ) 



3. Mandible. 



4. Maxilla. 



5. Maxillipede. 



FIG. 153. Dorsal surface of 

 cancriformis, From Bronn's 

 Thierreich. 



In the anterior region are the two com- 

 pound eyes, and behind them the 

 simple unpaired eye. The whip-like 

 outgrowths of the first thoracic ap- 

 pendage project laterally. 



Pre-oral. 

 Oral. 



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