238 BLSmNTS Off COMPARATIVE ZOOLOGY. 



a minute coiled tube (nephridium). These are the kidneys 

 of the worm, and each opens separately to the exterior 

 between the rows of setae. 



COMPAEISONS. 



With columns for Vertebrate, Arthropod, and Earth- 

 worm, answer the following questions : 



(1) Are paired appendages present ? 



(2) Do you find an evident body-cavity ? 



(3) Is the alimentary canal supported by a mesentery ? 



(4) Is the greater part of the nervous system dorsal or 

 ventral in position ? 



(5) Is there any segmentation visible from the outside ? 



(6) Is there anything which you could call internal seg- 

 mentation ? If so, what parts are repeated ? 



(7) Is there an external cuticle ? 



(8) Does the alimentary canal pass through the nervous 

 system ? 



(9) Is there an internal skeleton ? 



(10) Bumming up these points, what two forms do you 

 consider to be most similar ? 



(11) Draw transverse diagrams of a vertebrate, an 

 arthropod, and an earthworm, showing skeleton, body- 

 cavity, dorsal vessel, aorta, ventral vessel, heart, kidneys, 

 nervous system, appendages, etc., as far as you find them in 

 each. Which two seem most alike ? 



(12) Can you better bring all three diagrams into har- 

 mony by turning any one wrong side up ? If so, what one 

 must be turned ? 



(13) Can you recall any such connection, in any verte- 

 brate, between the dorsal and ventral blood-vessels, as you 

 find in the earthworm ? If so, where and what ? 



