ANOSTRACA 359 



phase of the movement. The food is agglutinated by a sticky secretion 

 produced by glands in the labrum, and pushed by the maxillules 

 between the mandibles, which pound it and pass it into the mouth. 



The organs of excretion are a pair of maxillary glands (p. 345), 

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

 They are wholly of mesodermal origin. The nervous system (Fig. 210) 

 and the vascular system have been described above (pp. 340 and 348). 

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

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

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



Fig. 239. A diagrammatic view of a Chirocephalus 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. 



Fig. 240. 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. 



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 con- 

 centration of salt, and some of its minor features change with the 

 degree of the concentration, so that it has been described under 

 different specific names. It differs from Chirocephalus in having only 

 six abdominal somites and in the form of the antennae of the male. 



