THE PHYLUM ANNELIDA 



two suckers being alternately attached and released. When unattached, the 

 animal may swim by sinuous, undulatory movements. 



Internally, the leech presents many modifications of the annelid structural 

 organization (Fig. 14.19). The digestive tract bears many pouch-like caeca 

 for the prolonged storage of ingested blood; the animal may go for long 

 periods without feeding. The coelom is much reduced, the cavity being 

 restricted to channels within a spongy meshwork of mesenchymatous tissue. 



Si 







4 



ji 



'b' 



i. 



^m^ 



Fig. 14.18. Class Hirudinea. A common fresh-water leech, Placohdella parasitica. A, dorsal 

 aspect; B, ventral aspect. Note the anterior and posterior suckers and the division of the 

 body into a larsje number of apparent segments. (From Master's Thesis of M. H. Woods, 

 1940, Cornell University.) 



419 



