20 FINGER- AND-TOE, OR OLUBBING. 



This division may go on until one amoeba has given rise to 

 hundreds. But by degrees each amceba becomes smaller and 

 smaller, and they would eventually die out. To counteract 

 this, what is known as "rejuvenescence " takes place. Eejuv- 

 enescence is the union or conjugation of two amoebfe, whose 

 protoplasm unites together, together with the nuclei, forming 

 one larger individual, which is again in a fit state to undergo 

 once more rapid division. This conjugation is really a kind 

 of primitive sexual reproduction, although there is, as far as 

 we can see, no difference between the conjugating individuals. 

 At least four species of amoebae are parasitic in man, and are 

 spoken of as Entania-ha , two of these are of no special account, 

 but the Aiiio'ha coli (Losch), and the Amwha TihtoJytira (Schau- 

 (linn), are. The latter is the cause of tropical dysentery, and is 

 found in man's intestines, and even the liver and kidneys. 

 None are so far known to attack animals or plants. 



Ebticulosa. 



The Eeticulosa are naked amo:'boid forms with slender, fila- 

 mentous, net-like pseudopodia. 



The well-known parasite of Finger-and-Toe or Clubbing 

 belongs here. 



FlNQEE-AND-TOB, OB ClUBBING. 



{Plasmodiophora hrass^inr. Woronin.) 



This disease occurs in cruciferous plants, both wild and 

 cultivated. It frequently causes great loss in turnips and 

 cabbage. The roots of the attacked plants and rootlets will be 

 found to be swollen and spindle-shaped and smooth, others as 

 large gnarled masses. The attack commences in the young 

 plants, from minute flagellulse released from the countless 

 spores in the soil entering the cells of the roots, where thoy 



