A MANUAL OF ZOOLOGY IB 



better for morphological work. Study specimen for a 

 right and a left side; a head and a tail; a ventral and a 

 dorsal surface. How are these details determined? Note 

 color. Would its mode of life suggest any jcause for the 

 color? Into how many regions can the body be divided? 

 Note the number of segments in each. The firmest part of 

 the body will naturally be the most muscular. Which 

 division is most muscular? Are the segments all alike? If 

 not, where do they differ? Look for a protective covering 

 (exoskeleton). Are there any special sense organs? Are 

 there any jointed appendages or legs? Make an outline 

 drawing pL_th.e_.first^ two divisions and put_in_the" exact 

 number of segments or^soffiilei;^ l^hTTight colored thlck- 

 enecf^lvlsioli is called the "girdle or clitellum. Note the 

 number of segments in it, and .whether they are complete 

 rings or not In numbering the segments from the" ante- 

 rior end, where do the segments of the girdle belong? 

 Prom a preserved specimen strip off a little cuticle. "Note 

 its color and texture. Mount, a small piece in water arid 

 study the structure with- the high power. Note the striae 

 and their direction. 



By passing the thumb and finger over th« sides of the 

 animal, sharp projections or setae will be detected. Study 

 with a hand lens and determine the direction and number 

 in each segment. -Note whether this direction is constant 

 throughout the whole length of the animal. With forceps 

 pull out a seta and study it with low power. Draw a seta. 



The prostomium is a projection on the extreme^nterior" 

 end of the animal, ventral to which the mouth will b6 

 found. In -numbering the segments the prostomium must 

 not -be counted. Note the anus at the extreme posterior 

 end. The dorsal- pores may be demonstrated by peeling off 

 the cuticle and examining it with the hand lens. How 

 many are there- on eg,ch segment? Are the segments- alike 

 In this respect? Look for a pair of openings external to 

 the ventral setae on the fifteenth segment;- the -opening of 

 the sperm ducts. ' Look for another- -pair in similar posi- 

 tion of the fourteenth segment; 'the openings of the ovi- 

 ducts. Two pairs of openings will be found in line with 

 the outer setae between segments 9 and 10, 10- and 11, one 

 pair in each groove; ■ the openings of the seminal recep- 



