PARASITES AND THEIR DEVELOP- 

 MENT. 



IF man is to be regarded as the favoured child of Nature, 

 and if it be held as true that life at large is subservient to 

 his sway and rule, it is no less true that he is liable to suffer 

 severely from the attack of certain of his lower neighbours, 

 and that he is despoiled in various fashions by some of the 

 most insignificant of living beings. Insects of various kinds, 

 insignificant as to size, but powerful beyond comprehension 

 in virtue of their numbers, devastate the crops which exercise 

 his mind and appliances in their cultivation. And after the 

 crops have been duly stored and garnered, the labour of 

 months and the full fruition of the farmer's hopes may be 

 destroyed by the insidious attack of granary-pests. Plants 

 of lowly grade, minute fungi and like organisms, person- 

 ally known to the microscopist alone, blight at once the 

 prospects of the agriculturist and of his cereals. A minute 

 fungus, burrowing its way within the tissues of the potato- 

 plant, has ere now brought destitution and famine on a 

 nation, and still causes disease amongst our tubers to an 

 extent which none but our potato-growers can fully realise. 

 Nor is the farmer's sphere singular in respect of its liability 

 to the attack of animal and plant foes. Parasites, the com- 

 plexity of whose life-history almost defies belief, invade the 

 stock of the breeder of cattle and sheep and decimate his 

 flocks ; whilst these same parasites may occasionally invade 

 the human domain itself, and cause disease and death to 



