2l6 



THE CRAYFISH. PHLYUM ARTHROPODA 



REPRODUCTION 



The sexes of the crayfish are separate. The generative organs 

 He in the thorax, above the gut and below the pericardium. They 



Pig 1^7, — The reproductive organs of a female crayfish. — After Suckow. 



od Oviduct ; ov., ovaries ; ov'., fused posterior part (median lobe) ; vu., female aperture on the second 

 "' ' walking leg (p^). 



have the same general shape in the two sexes, consisting of three 

 lobes, two anterior and one posterior, with a pair of ducts, which 



start from the junction of the anterior 

 and posterior lobes and run to openings 

 on walking legs. The ovary (Fig. 147) 

 is larger and broader than the testis, 

 and has an internal cavity into which 

 the eggs are shed. The oviducts are short, 

 straight, and wide ; they open upon the 

 coxopodites of the second pair of walk- 

 ing legs. The testes (Fig. 148) consist of 

 a number of branching ducts which end 

 in small alveoli, in which the sperma- 

 tozoa are formed. The vasa deferentia 

 are narrow and much coiled ; their 

 first part is very slender and translucent, 

 the second part, which forms most of 

 the duct, is wider and glandular, and 

 a short terminal region has muscular 

 walls which force out the sperm. The 

 spermatozoa (Fig. 149) are relatively large discs about 15 microns 

 in diameter, with stiff, pointed processes round the edge. The 

 nurlf^iis is a round capsule and to one side of this is a small, 



Fig. 148. — The reproductive 

 organs of a male crayfish. 

 — After Huxley. 



t. Testes ; vd., vas deferens ; vd', open- 

 ing of vas deferens on last walking 

 leg. 



