CRAYFISH 409 



laying, they pass out through the oviducts. The male reproductive 

 organs are composed of the bi-lobed testis located dorsal to the pyloric 

 stomach and ventral to the heart. Spermatogenesis takes place here 

 and mature spermatozoa are shed. The tubular vasa deferentia ex- 

 tend posteriorly and ventrally to open externally on the coxopodite 

 of each fifth walking leg. During copulation (mating) the sperm 

 cells are transferred by the two pairs of anterior swimmerets (pleo- 

 pods) of the male from the apertures of the vasa deferentia to the 

 annulus (seminal receptacle) on the ventral side of the thorax of 

 the female. When the mature eggs are later laid, they are likely 

 fertilized as they pass posteriorly in the groove between the legs on 

 the two sides of the body. The fertilized eggs are cemented to the 

 swimmerets hy a secretion and appear much as small bunches of 

 shot-sized grapes hanging there. The later development continues 

 here, and they are aerated by movements of the swimmerets through 

 the water. 



Cleavage divisions follow over the surface of the egg and the em- 

 bryo develops on one side of the mass. The body form with segments 

 and limb buds appears, and hatching occurs in from five weeks to two 

 months. The larvae grasp the swimmerets with their chela and re- 

 main with the mother for about a month. Two or three davs after 

 hatching they pass through the first molt or ecdysis; that is, they 

 shed the outer cuticle. This is repeated seven or eight times during 

 the first season to allow for growth. The average life span of the 

 crayfish that reaches maturity is about four years. 



Regeneration and Autotomy 



This power is limited to the appendages and eyes in this animal, 

 but it is quite well developed in these parts. The possibilities and 

 rate of regeneration are greater in younger animals. Mutilated or 

 lost legs or mouth parts are readily restored. 



The genus Cambarus has the ability to allow a walking leg to 

 break off at a certain line or joint if it is caught or injured. A new 

 leg will develop from this stump. This phenomenon is called autot- 

 omy. There are special muscles to help in this and a membranous 

 valve stops the passage of blood through the leg, thus preventing ex- 

 cessive bleeding. Bleeding will stop more quickly if the break oc- 

 curs at such a point than it would otherwise. Autotomy often makes 

 it possible for the animal to sacrifice a leg to save its life. 



