LEPIDONOTUS 97 



tacles, and a pair of fleshy palps. Outside the palps are two 

 pairs of cirri arising from the peristomium. The significance 

 of these will be understood later. 



3. Find the mouth, placed ventrally in the first or per- 

 istomial somite. The mouth leads into a buccal region, which 

 is eversible and fringed at the end with papillae, each having 

 a dark spot at the base. If the pharynx is retracted, expose 

 the buccal cavity by a median ventral incision. In the an- 

 terior end of the pharynx are four black chitinous jaws. Do 

 you infer that this species is carnivorous or herbivorous? 

 The eversible buccal region and the protrusible pharynx form 

 the proboscis. 



4. The anus is dorsally placed, and can be found beneath . 

 the notches in the last pair of elytra. 



5. Examine the lateral appendage or parapodium of the 

 third or any subsequent somite. Note that it consists of a 

 stout ventral or neuropodial division, and a less prominent 

 dorsal or notopodial division, each supported internally by 

 a chitinous rod or aciculum, and bearing externally a tuft 

 of setae. If there is time, compare the form of the noto- 

 podial and neuropodial setae. The typical parapodial struc- 

 ture is completed by a soft neuropodial cirrus ventrally, and 

 a notopodial cirrus dorsally. Did you find any evidence that 

 the elytra are modified notopodial cirri? 



6. Make a careful study of the appendages of the first or 

 peristomial and the last or anal segment. Cut off close to 

 the body, mount in glycerin, and examine with low power of 

 the microscope. Determine the homology of the parts ob- 

 served. 



Draw the dorsal aspect of the ^head, to show the appen- 

 dages and the proboscis, if exposed. Diagram the structure 

 of the parapodium as seen in a transverse section of the body. 



Unlike most other worms, many of the Aphroditidae have 

 a fixed number of somites. Count the number in your speci- 

 men, including in the enumeration the peristomial and anal 

 segments. How many pairs of elytra? The number and po- 

 7 



