52 LEECHES 



from the epidermis but it does not reduce water loss very appre- 

 ciably. Klekowski (1961) kept Hirudo and Haemopis in air of 

 80% relative humidity at 22°C and found that their water content 

 was reduced to 20% in 4-5 days, after which death ensued. If 

 returned to the water after about 4 days they were able to return 

 to full hydration within a few hours. A more drastic process of 

 desiccation was carried out by Hall (1922) on the rhynchobdellid 

 leech Placohdella parasitica. When a current of dry air was passed 

 over these leeches they lost 92% of the water in the body m 7 J hr, 

 but recovered when placed in water at 13°C. 



