The American Museum Journal 



Vol. IX MAY, 1909 No. 5 



THE SERIES OF PROTOZOAN MODELS. 



THE minute one-celled organisms known as Protozoa form a 

 group of immense importance both from a biological and an 

 economic standpoint. Swarming in countless millions in both 

 fresh and salt water, and at times even in the bodies of other animals, 

 they are the most abundant and most widely distributed of all life. 

 Many of the smaller marine and fresh water creatures depend upon 

 them for food, and among them may also be found some of the most 

 important disease-causing parasites. The calcareous and siliceous 

 skeletons of others settle to the sea bottom by thousands as the animals 

 die, to collect in layers often many feet in thickness. The calcareous 

 skeletons sometimes become compacted into solid rock, and thus are of 

 great geological importance, many extensive cliffs of lime-stone and 

 chalk having been formed in this way. The siliceous skeletons form 

 the so-called "Radiolarian ooze," which is the source of the "Barbados 

 earth" used in manufactures for polishing and grinding, and which 

 forms no inconsiderable part of the island of Barbados. Though this 

 vast world of creatures is so important and surrounds us on every side, 

 penetrating, as it were, all the interspaces between the larger forms of 

 life, yet it is invisible to our eyes, and were it not for the compound 

 microscope, we should be absolutely ignorant of it, except in its effects. 

 The Museum is at present completing its series of greatly enlarged 

 models of the typical Protozoa, and one of the most striking of these has 

 recently been finished for exhibition. It is shown in the accompany- 

 ing illustrations (pages 104 and 105). This Protozoan (Auloceros ele- 

 gans Hackel) belongs to the group Radiolaria, so called because of the 

 radiating siliceous or glassy skeleton which characterizes these forms. 

 Sometimes these are of great complexity and beauty, and though the 

 Protozoa as a whole are the simplest in structure of all animals, being 

 composed of but a single cell, certain forms among the Radiolaria attain 

 considerable complexity of intracellular structure, as may be seen in the 

 figure. 



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