MOLLUSCS. 245 



of blood. Their wool gets dry, and does not hold 

 together, and they become emaciated. Dropsy and 

 diarrhoea set in, and jaundice often makes its appear- 

 ance. If a sheep is infested by a tolerably large 

 number of flukes, death is almost always the final 

 result. 



" The best preventative is a trustworthy and careful 

 shepherd," ^ who will not let the sheep feed in spots 

 where previous experience shows the disease is 

 usually contracted during damp summers. Further- 

 more, sheep badly infested should be slaughtered as 

 soon as possible, so that the flukes they contain may 

 not get to the egg-laying stage. Sick sheep should 

 be fed with nourishing food (various kinds of hay, 

 oats; with addition of cooking salt), so that young 

 sheep containing but few flukes may get back their 

 strength, while this treatment will make the badly 

 infested sheep die more quickly. 



Oxen are also frequently aflected by fluke disease 

 in many regions, other animals to a less extent. 



The Small or Lancet-shaped Liver Fluke {Distoma 

 lanceolatum) 



is about three-eighths of an inch long, one-tenth of 

 an inch broad, thin, and lancet-shaped. Lives, like the 

 preceding kind, in the liver of the sheep. Develop- 

 ment unknown. 



Fourth Sub-Kingdom : MOLLUSCA (Molluscs), 



This sub-kingdom, to which oysters, snails, cuttle- 

 fish, etc., belong, includes unsegmented animals devoid 

 of internal skeleton, and with bilaterally symmetrical 

 (p. 16) embryo, while the adult maybe much modified, 

 especially in snails, which are enclosed in spiral shells, 

 and also have their bodies partially coiled. The skin 

 of molluscs possesses a peculiar and characteristic 

 ' Spinola. 



