84 ANNELIDA. 



blood. There is only one internal septum and it forms a so- 

 called diaphragm. Anterior to the diaphragm the nephridia 

 are large and excretory in function. Posterior to the diaphragm 

 the nephridia serve as genital tubes. 

 A drawing is desirable. 



CISTENIDES GOULDII. 



This very aberrant worm belongs to the family Amphictenida3. 



1. Study the beautiful tube of sand and the manner in which 

 the grains are fitted together. It is said that the worms can 

 carry the tubes about. 



2. See how the peristomium and the large golden setce close the 

 shell. The setae are said to belong to the second somite. Notice 

 the ends of the tentacles protruding from the tube. 



3. Find the tentacles, two pairs of gills, and the parapodia. 

 Notice how the latter diminish in size posteriorly and how each 

 typically consists of a ridge-like notopodium without setae and a 

 reduced neuropodium with long golden setae. If the specimen is 

 complete you can see a much degenerated portion (the scapha) 

 at the posterior end, which serves to close the small end of the 

 tube. 



A drawing is desirable. 



CLYMENELLA TORQUATA. 



This worm belongs to the family Maldanidae. It makes 

 tubes of sand and generally lives in sheltered places on sandy or 

 muddy shores. 



1. Study the structure of the tube; observe how the animal 

 protrudes at either end of the tube. 



2. Observe the diameter and length of the worm, the small 

 number of somites, their great length as compared to somites 

 of Nereis, and the reduced parapodia provided with simple setse. 

 Notice the characteristic collar on the fifth somite, and the 

 funnel at the posterior end, with the anus within it. The mouth 

 is more or less ventral and is overhung by a narrow prostomium 

 surrounded by a peristomial rim. 



A drawing is desirable. 



