94 



THE SMALLEST LIVING THINGS 



tons par excellence of the animal kingdom. Others are occa- 

 sional feeders. Continuous feeders, so called, are those forms 

 of ciliated protozoa with a permanently open mouth toward 

 which a current of water, bearing bacteria and other minute 

 forms, is constantly directed by the action of cilia about the 



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&. V > 1 1 J/ <; ; ' . 'W ~ 



Fis 



-FOOD GETTING BY TRAPPING 



Allogromia oviforme, a common marine shore-dwelling 

 foraminiferon with a chitin shell (S) and one mouth- 

 opening through which there is a constant streaming of 

 protoplasm. A diatom, D, has just been captured in the 

 pseudopodial network 



After M. Schultze 

 Magnification, 50 



mouth. After passing through the mouth the water and food 

 are collected in a vacuole which, upon reaching a certain size, 

 is carried away from the region of the mouth by protoplasmic 

 movement. Such vacuoles are known as gastric vacuoles or im- 

 provised stomachs, for while in them food substances are di- 

 gested by means of digestive ferments that appear in the vacuole. 



Occasional Feeders 



Occasional feeders eat whenever chance brings prey within 

 the radius of their activity, and many of them are guilty of feed- 

 ing, at times, upon their close relatives! In some species bal- 

 loon-like membranes are spread out like sails for directing the 

 food currents toward the mouth. In Foraminifera, net-like traps 

 of pseudopodia are spread out for the capture of larvae, dia- 

 toms, and smaller protozoa (Fig. 54). The most spectacular 

 forms, however, are those which capture and paralyze living prey 



