196 



ZOOLOGY 



The economic importance of parasitic worms is very great. 

 Thus, although no great e]3iclemics of the flukes have occurred 

 in this country, a million shee]5 are annually lost by this para- 

 site in Great Britain ; and in 1879 and 1880 it was estimated 

 that three million sheep died annually in England alone of 



- Development of Distomum 



porocyst eon- 



taining developing rcdiae ; C, redis, containing a daughter redise and embrj'O 

 liver-flukes ; D. tree-swimming, tailed lar\-a of liver-fluke ; 6. op, birth 

 opening ; cnt, food canal of rcdia ; eye. eyespots ; gust, young redia : fjerm, 

 inor. early stages in formation of the embr>'o livei-fluke : int. intestine of 

 larval liver-fluke : ii:x. resophagus ; m. xii. oral sucker: yiop. head papilla of 

 ciliated larva, A ; ]>h. pharnj-x ; pruc, ijroccsscs of redia ; vttd. su, ventral 

 sucker. After Thomas. 



this parasite. In Bumios Ayres, during 1882, a million sheep 

 died of fluke disease. By great care in preventing infection, 

 especially during dami^ seasons, we may be able to prevent any 

 such disaster in this country. 



