148 ELEMENTARY BIOLOGY. [CHAP. 



Each is a dark green mass, on the exterior of 

 which minute rounded eminences (indications 

 of the contained ova) can be seen. Near 

 their anterior ends they lie in contact in the 

 middle line, and for a short distance their 

 substance is continuous. 



f. An oviduct arises from each ovary a little in 

 front of its middle, and passes directly to the 

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



14. Alimentary organs. 



t?. 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 ccecal 

 diverticulum close to the stomach, and in the 

 lobster one near the anus. 



c. Examine the liver. 



. It is an elongated soft pale-yellow mass lying 

 in each side of the cephalo-thorax, and opening 

 by a duct on each side at the point where the 

 intestine joins the stomach. 



/?. Tease out a bit of the liver in water; it is 

 made up of branched ccecal tubes, which when 

 examined microscopically are seen to be lined 

 by a layer of cells (epithelium). 



