MYSIS. TALORCHESTIA. 141 



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 mil be profitable. 



8. Trace the genital ducts to their external openings. 



MYSIS. 



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. What are their posi- 

 tions? 



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. 



TALORCHESTIA. (Beach-Flea.) 



These active little animals inhabit sand beaches, where they 

 burrow in the sand and hide in the decaying vegetable matter 

 that accumulates along such beaches near high-water mark. 

 Turn over some of this material and notice the activity of the 

 animals that are disturbed. Most of them probably belong to 

 another closely related genus, but their movements are much 

 the same. How far can a specimen leap? Are the leaps of an 

 individual continuously in one direction, so it may get away 

 from the point of danger ? Is each leap straight forward or does 

 the animal whirl in the air? What purpose is served by the 

 leaping? Try to catch a specimen. Determine how the leaping 

 is accomplished. Determine how the specimens burrow. 



