170 ARTHROPODA. 



region of the antepenultimate thoracic segment. Remove the 

 ovaries, deferring the tracing of the oviduct. 



4. Beneath the reproductive organs is the granular liver. 

 This consists of two lobes which extend from the stomach 

 to the end of the telson. They form saccular diverticula 

 between segments and in the telson. Where do they open into 

 the alimentary tract? 



5. Free the intestine, which is between the lobes of the liver. 

 The rectum is in the sixth abdominal segment. 



6. Pull back the anterior end of the stomach, identify the 

 circum-esophageal connectives, in order not to destroy them, 

 and free the stomach by cutting the esophagus and intestine. 

 Examine the stomach under water. 



7. Trace the nerve chain. What ventral ganglia are fused? 

 The cerebral ganglia are most easily exposed by slicing away, 

 very superficially, the dorsal surface of the rostrum and pressing 

 the eye muscles apart. 



A drawing of the nervous system will he profitable. 



8. Trace the genital ducts to their external openings. 



MICHTHEIMYSIS (OR HETEROMYSIS). 



If living specimens are to be had, watch them swim, and de- 

 termine what parts are used in swimming. Does the animal 

 swim in one direction or in both? 



1. Compare the body with that of a lobster. 



2. Are appendages present on each of the divisions of the 

 body? Compare them with the appendages of the lobster? How 

 do the thoracic appendages differ? 



3. Notice the otocysts in the tail fin. 



4. The living animal is transparent, and many internal 

 organs, such as heart, gills, and portions of the alimentary 

 canal, can be seen. 



// time permits, make a drawing. 



Bergh: Beitrage zur Embryologie der Crustacean. Zool. Jahr. (Anat.), 

 6, 1893. 



