LIFE, IN ITS LOWER FORMS. 



but if it pass into the carnivorous animal, it becomes 

 Cestoid. 



Besides " the staggers," our sheep-farmers are but too 

 familiar with a disease that occasionally decimates their 

 flocks, and which they term "the rot." It chiefly attacks 

 the sheep when pastured in low wet meadows, and is 

 caused by the excessive multiplication of a worm known 

 as the Fluke (Distoma hepaticum), which infests the livers 

 of these and other animals. It resembles a minute sole, 

 about an inch long, with a sucking disk at each end, each 

 of which was formerly supposed to include a mouth 

 (whence the name " double-mouth ;") but the posterior 

 one has been ascertained to be a simple imperforate 

 sucker. From the true mouth proceeds a single digestive 

 canal, which soon divides into two main stems, one pass- 

 ing down each side, and giving off secondary ramifications 

 as they proceed, which branch like the Augers of a hand, 

 or the twigs of a shrub, and thus spread over the whole 

 body. As all the branches are ordinarily filled with dark 

 bilious matter, they can be distinctly seen within the 

 pellucid white flesh, forming two beautifully ramifying 

 trees. 



Closely resembling the Fluke in their soft gelatinous 

 flesh, their flattened form, and the ramification of their 

 digestive canal, are the little worms called Planarics, that 

 are found in great numbers on the submerged vegetation 

 of our rivers and ponds. They are generally minute and 

 black ; but we have some marine species on our coasts 

 that are much larger, and are ornamentally tinted, 



" These creatures, notwithstanding their apparent help- 

 lessness, are found to live on worms or insect larvce ; 



