94 ANNELIDA. 



dorsal or notopodial division, each supported internally by a 

 chitinous rod or aciculum, and bearing externally a tuft of 

 setse. If there is time, compare the form of the notopodial 

 and neuropodial setse. The typical parapodial structure is 

 completed by a soft neuropodial cirrus ventrally, and a noto- 

 podial cirrus dorsally. Can 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 observed. 



Draw the dorsal aspect of the head, to show the appendages 

 and the proboscis, if exposed. Diagram the structure of the para- 

 podium 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 specimen, 

 including in the enumeration the peristomial and anal segments. 

 How many pairs of elytra? The number and position of the 

 elytra are also characteristic of various genera, and may be 

 conveniently represented by an elytral formula consisting of 

 the numbers of the somites on which elytra are borne, e. g., 

 2, 4, 5, etc. Determine the elytral formula of your specimen. 

 DraiD one of the elytra, noting its form, surface, and border 

 markings, etc. These points are of importance in defining 

 species. The last pair of elytra are notched on the median 

 side over the anus, which in this form opens dorsally instead of 

 terminally. 



DIOPATRA CUPREA. 



This worm belongs to the family Eunicidse. Specimens 

 live on mud- and sand-flats, sometimes above low-tide mark, 

 but usually where the burrows are covered by water. This 

 form is especially interesting because of its feeding and tube- 

 building habits, parapodial gills, and complex jaw-apparatus. 

 Study the preserved specimens for the structure and specimens 



