AN ATTEMPT TO CLASSIFY EARTHWORMS. 285 



ovisacs are dotted ; the sperraathecse are outlined ; and the 

 prostate and sac with penial setae are also represented in 

 outline. 



In the alimentary canal^ the extent of the buccal cavity as re- 

 presented is not intended to indicate the actual extent, as we 

 have no sufficient data for determining this point ; hence the 

 position of the commencement of pharynx is hypothetical ; but 

 its posterior limit is true in most cases, although in many genera 

 this point is left vague in the drawings and descriptions of 

 authors : the limit here assigned is, in these cases, deduced 

 from analogy with better known genera. The gizzard is 

 indicated by its thicker outline, and by the transverse line in 

 front and behind it. 



In the excretory system the black dots represent the funnels, 

 the thicker line the " duct," and the narrow wavy line the 

 coiled tube : there is no attempt to indicate the arrangement 

 of this coil. In the " plectouephric " genera the short lines 

 are intended to indicate the passage of the duct through the 

 body-wall to the exterior. The external openings are shown 

 in the lowermost diagram as small circles,^ the setse as short 

 lines, and any genital aj)ertures as black dots. In cases where 

 the nephridiopores are not indicated their arrangement is not 

 known. 



The representation of the excretory system is purely con- 

 ventional, especially in forms with " tufts " or network, and 

 merely serves to indicate whether the genus is " plectouephric " 

 or " meganephric,^' and in the latter case whether the duct is 

 '^simple" or '' csecal." 



The modification of the anterior nephridia or excretory net- 

 work to serve to moisten the food, and act as '^pepto-nephridia," 

 is indicated. 



The diagrams represent the worms slit open along the middle 

 line of the dorsal surface, and cut edges of the body-wall pinned 

 aside. 



* Unfortunately the " process " has in many cases not reproduced the 

 circle, so that the nephridiopores appear as small black dots. The index 

 lines, too, are often not reproduced. 



