APPENDIX TO CHAPTER IX 



143 



tinguislied, the Endoprocta (Fig. 

 128), iii which the individual consists 

 of a long stalk and a " head " or 

 body proper ; and the Ectoprocta 

 (Figs. 129-131), usually without 

 such a stalk. The Ectoprocta are 

 the prevailing type. The marine 

 species form lace-like mats on sea- 

 weed or stand up as branching, bushy 

 colonies (Fig. 129). Some of the 

 fresh- water forms make loose, antler- 

 like colonies (Fig. 130), while others 

 lie on the surface of a more or less 

 spherical mass of jelly which they 

 have themselves secreted (Fig. 131). 



FIG. 131. Pectinatella magnified, a dense complex of colonies, growing upon 

 a stick. Each star-shaped group represents a single colony. One-half uat. 

 size. Photo, of living mass by W. H. C. P. 



APPENDIX TO CHAPTER IX 



KEY TO THE PRINCIPAL SPECIES OF EARTHWORMS OF THE 

 UNITED STATES 



a\. Clitellum begins on segment xiii or xiv ; $ pore, 

 on segment xviii or xix ; 2 gizzards in segments 

 v and vi. 



61. 2 dorsal vessels ; lives in soil of prairies 



6 2 . 1 dorsal vessel ; lives in river-bottom land 



a-2. Clitellum does not begin in front of segment xviii ; 

 $ pore on segments xii and xiii, or (usually) xv. 

 61. Prostomium incompletely divides buccal lobe 

 [genus Allolobophora]. 



( Diplocardia 

 \ communis 

 D. riparia 



