142 ELEMENTARY BIOLOGY. 



-7. Tease out a bit of the testis in water and ex- 

 amine with J obj. for spermatozoa. They are 

 motionless, and consist of an elongated cell from 

 one end of which three rigid pointed processes 

 radiate. 



8. The ovaries of the lobster are also elongated 

 and lie partly in the thorax and partly in the 

 abdomen, above the alimentary canal (14). 

 ' Each is a black mass, on the exterior of which 

 minute rounded eminences (indications of the 

 contained ova) can be seen. Near their ante- 

 rior ends they lie in contact in the middle line, 

 and for a short distance their substance is con- 

 tinuous. 



e. An oviduct arises from each ovary a little in 

 front of its middle, and passes directly to the 

 genital opening of its own side (1. c. 7.). 



14. Alimentary organs. 



a. Remove the dorsal part of the carapace in front 

 of the cervical suture, and there will then be 

 laid bare, in front of the position of the heart, a 

 large sac the stomach ; pass a probe into it along 



/.. .the gullet, through the mouth- opening which lies 

 between the mandibles. 



b. Trace back the tubular intestine from the stomach 

 to the anus. It dilates near the latter in the 

 lobster. In the crayfish it presents a small caecal 

 diverticulum close to the stomach, and in the 



. . -| lobster one near the anus. 



c. Examine the liver. 



a. It is an elongated soft pale-yellow mass lying 

 in each side of the cephalo-thorax, and opening 



