CRAYFISH 407 



they are crushed by the mandibles. Mastication continues in the 

 cardiac chamber of the stomach and chemical digestion begins in 

 the pyloric portion. The digestive juices possess enzymes which 

 convert the food into soluble form, and as it passes along the in- 

 testine, it is absorbed by the blood and distributed to the tissues 

 over the body. This conversion of food material into protoplasm is 

 assimilation. The external phase of respiration has put oxygen in 

 the blood, and it is distributed throughout the protoplasm of the 

 cells. The energy stored in the food material is released or converted 

 to kinetic form by union with the oxygen (oxidation) in the proto- 

 plasm. From this union there is excess heat produced. Mechanical 

 and chemical activity is the result of the harnessing of this energy. 

 As a by-product of this cataholism, excretory materials, such as excess 

 water, urea, uric acid, and other substances are formed in solution 

 and are collected by the blood. The green glands relieve the blood 

 of these and deliver them to the exterior. Of course growth results 

 when excess food materials are built into the cells at times when 

 the rate of anabolism exceeds that of catabolism. 



Reproduction 



These animals are dioecious (sexes separate) and the mating takes 

 place either in the spring or fall or perhaps both. The spring hatch 

 become well developed before winter. The eggs fertilized in the 

 fall may not be laid before spring. 



In the case of Camharus clarkii the adults retire to holes or bur- 

 rows at the water's edge during the summer. It is here that the eggs 

 are laid and carried by the female until after hatching; then the 

 young cling to her swimmerets. In late summer or fall, soon after 

 the young hatch, the adults become very migratory at night, particu- 

 larly in rainy weather. In this way they help to distribute the young 

 to new water holes. 



The feynale reproductive organs are composed of a bi-lobed ovary 

 located beside the pyloric chamber of the stomach and beneath the 

 pericardial sinus. During development the eggs appear in the ovary. 

 Two oviducts lead, one from each side of the ovary, to a genital pore 

 in the coxopodite of the third w^alking leg (pereiopod) of each respec- 

 tive side. The ova develop in follicles in the ovary. The maturation 

 divisions (oogenesis) take place here and, when mature, the eggs 

 break into the central cavity of the ovary, from which at the time of 



