ANOSTRACA 



321 



they are carried forward to the mouth by a minor stream which is said 

 to be caused by the escape forwards at the bases of the Umbs of some 

 of the water contained in the lateral chambers at a certain phase of the 

 movement. The food is agglutinated by a sticky secretion produced 

 by glands in the lab rum, and pushed by the maxillules between the 

 mandibles, which pound it, into the mouth. 



The organs of excretion are a pair of maxillary glands (p. 309), 

 situated in the hinder part of the head and the first thoracic somite. 

 They are wholly of mesodermal origin. The nervous system (Fig. 199) 

 and the vascular system have been described above (pp. 303 and 311). 



Fig. 228. A diagrammatic view of a Chirocephalns swimming on its back. 

 The arrows show the direction of the currents set up by the action of the 

 thoracic limbs, the dotted line the course of the gathered particles in the food 

 groove. Partly after Cannon. 



Fig. 229. Thoracic limbs of Chirocephalus seen from the median side in two 

 phases of their action. A, The forward stroke: water is being drawn through 

 the fringe of bristles into the space between the limbs, which is enlarging. 

 B, The backward stroke : water is being driven backwards out of the space 

 between the limbs, which is contracting. 



The gonads are a pair of tubes lying one on each side of the alimentary 

 canal in the abdomen, ^nd are continuous in front each with a short 

 duct. The vasa deferentia lead to the penes, the oviducts to a median 

 uterus in the egg pouch. The eggs are enclosed in stout shells and 

 will remain alive in dry mud for many months. The larva at hatching 

 is a late Nauplius in which, though there are no appendages behind 

 the mandibles, the trunk is already distinct from the head. 



Artemia salina, the other British species of anostracan, occurs in 

 various parts of Europe in salt lakes and marshes and in pans 

 in which brine is being concentrated. It can endure a very high 



