54 ///. ARTIFICIAL KEY FOR THE 



(a) Appendages consist of fleshy, jointless lobes, 

 beset with bristles; or else of the bristles 

 alone, arranged in paired lateral groups. 



Annelides. 



{b) Appendages jointed, and usually differentiated 

 into various sprts of limbs, with different 

 functions Arthropoda. 



(c) Appendages none; suckers at ends of body, 

 which is flat and very finely segmented. 



Hirudinea, sub Annelides. 



{d) Appendages none ; body composed of ' ' links ' ' 

 which increase in length posteriorly, and 

 which have the appearance of somites; geni- 

 tal pores on edges of links; anterior end 

 head-like, but with no mouth; usually 

 equipped with hooks and suckers. 



Cestodes, sub Vermes. 



2. Body segmentation not really external, but marked 



in the muscular system in the form of V-shaped 

 lines which are seen through the transparent skin. 

 No head, but pointed at both ends. 



Amphioxus, sub Prevertebrata. 



3. Body segmentation not apparent externally, but 



marked in the muscles of the trunk and in the 

 trunk portions of the internal skeleton ; two pairs 

 of paired limbs, one or both of which may be 

 reduced. Vertebrata. 



4. Body unsegmented (at least apparently so). 



{a) Colonial, i.e. animals in groups, with organic 

 connection between them or between their 

 skeletal supporting structure. All aquatic. 

 * Sessile, aquatic. 



f Each animal in a " cell " into 

 which it may be withdrawn; 

 ciliated tentacles around the 

 mouth. Marine and in fresh 

 wader. . . .Bryozoa, sub Vermes. 



