PHASCOLOSOMA. 95 



3. Study the egg-strings which are lodged in the tube, and 

 the young embryos which are to be found in the brood-pouch. 

 A drawing is desirable. 



GEPHYREA. 



PHASCOLOSOMA. 



This form is commonly found buried in sand between tide- 

 marks. Specimens sometimes occur on the same flats with 

 Nereis, but they are generally more abundant where the mud is 

 of a slightly different, more sticky character. 



1. Handle a living specimen and see how turgid it is. If 

 you touch a specimen that has been allowed to expand in a dish 

 of sea-water you will find it is rather soft, but becomes turgid 

 immediately upon being touched. How is this accomplished? 



2. Examine a living animal in a dish of sea-water. The 

 anterior portion of the body, the introvert, is drawn in, but may 

 occasionally be extended, when it will be seen to bear at the 

 anterior extremity a crescentric crown of tentacles, which partly 

 surrounds the mouth. 



3. Compare with a preserved specimen which has been killed 

 with the introvert extended. 



Make drawings showing the animal with the introvert pro- 

 truded and with the introvert concealed. 



4. The anus is located on a dorsal papilla, anterior to the 

 middle of the body. Near the anus a pair of lateral papillae 

 mark the position of the nephridiopores. The coiled intestine 

 and brown nephridial tubes can probably be seen through the 

 body-wall. Note carefully the character of the skin. Is there 

 any indication of spines, appendages, or eye-spots? 



For dissection use both fresh and preserved specimens. 

 With scissors open the worm from end to end near the mid- 

 dorsal line, and pin the body-wall out flat. 



5. In opening the fresh worm, note the pinkish ccelomic 

 fluid which fills the ccelom. Examine a drop under the micro- 

 scope. What functions has this fluid to perform? 



