PHASCOLOSOMA. 109 



6. Behind the vagina opposite the openings on the ventral 

 side are the four mucous glands. 



Draw. 



7. Nervous System. — The location of the ventral cord has 

 already been noticed. Find — 



(a) The number of ganglia. 



(6) Whether the ganglia are of equal size? Do they all give 

 off the same number of lateral nerves? 



(c) The supra-esophageal ganglia, above the pharynx. 



(d) The connectives that join the supra-esophageal ganglia 

 to the first pair of the ventral chain, the infra-esophageal ganglia. 



(e) The nerves that run from the supra-esophageal ganglia 

 to the eyes. 



(/) There are three stomo-gastric ganglia, one on each side 

 of the muscular lobes of the buccal pouch and one on the median 

 line. These are joined to the supra-esophageal gangUa. 



Draw the nervous system. 



8. Open the buccal cavity by cutting along one side and 

 notice the three large buccal muscles, one dorsal and two 

 lateral. These bear many minute denticles that may be seen, 

 in the right position, with a compound microscope. It is by 

 means of these that the leech makes its wound. 



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 



