THE DRAMA OF LIFE 23 



Mr. Hudson's very instructive picture of a wave of life in 

 South America. Fine weather and many blossoms ; many 

 flowers and many bees ; many bee-grubs and many mice ; 

 multitudes of mice and a thronging host of birds of prey. 

 Diets are changed, habits are changed, numerical propor- 

 tions are changed ; and then the season suddenly changes, 

 and everything collapses with terrific mortality into a new 

 position of equilibrium. 



Rotifers, or Wheel-animalcules, are microscopic, but the 

 struggle for existence is as keen as among rats. Most eat 

 single-celled plants and animals ; some pierce the cells of 

 Algae and suck out the living matter ; and some swallow 

 other Rotifers whole. Mr. C. F. Rousselet, whose beautiful 

 microscopic preparations of Rotifers are deservedly famous 

 both in Europe and America, has told us of the cannibalistic 

 voracity of Ploesoma hudsoni, which seems actually to 

 have a predilection for its own kith and kin. ' Of all 

 Rotifers this is the most vigorous swimmer ; it rushes 

 through the water at great speed, snapping at any other 

 Rotifer that comes in its way, carrying it in its mouth 

 and devouring it without a moment's pause '. ' The 

 attacking individual snaps at and holds on to its victim like 

 a bull-dog ', it pierces the skin and sucks up the soft parts. 

 One of Mr. Rousselet's slides showed three of these ' atro- 

 cious cannibals ' : ' the anterior individual is being carried 

 in the jaws of its captor, whilst the latter has been caught 

 a moment later by a third Ploesoma, intent on devouring 

 both '. We have here a good instance of the frequent 

 intensity of the struggle for existence. 



Thrust and Parry. We get a side-light on the struggle 

 for existence when we observe the prevalence of armour 

 and weapons, and all manner of defensive and offensive 



