(THE YOUNG NATURALIST. 



21 



• ne of these called pretomim has recently 

 |;en found in the Canary Islands as an 



• ■ange slime covering the backs of certain 

 ; tells; it is globular in shape, and throws 



• it numerous pseudopodia which act as 

 j ms to catch little bits of matter suitable 



r food. These bits of matter are grad- 

 lilly drawn into the animal at any part, 

 j having no mouth any portion of the 

 jiimal can fulfil that office at will. They 

 te reproduced by fission, that is, by 

 jilitting in two, and each half producing 

 I distinct individual. 



Theamre l xe issue short blunt pseudopodia. 

 I tiey have a nucleus, and one or more 

 i ntractile vesicles. A contractile vesicle 

 I a hollow part of the body filled with 

 Ime fluid which may be water or some 

 Ind of digested food, the vesicle suddenly 

 Infracts, sending the fluid to various parts 

 I the animal, opening and contracting in 

 lis way at intervals ; and this seems to 

 j the first rudiments of a circulatory sys- 

 |m. It is questionable whether the arm bee 

 lie distinct animals, as many of the higher 

 jganisms pass through the same stage and 

 ,Je scarcely separable from aracebce. Some 

 i them develop a sort of hard case, which 

 isms to connect them with the next class, 



magnified. 



} Foraminifera, which are little organisms 

 tich develop shells or coverings composed 

 carbonate of lime. Some live in fresh 

 8 ter, but the great majority live in the 

 * ; they are chiefly interesting as having 



Gromia Oviformis, one of the Foraminifera, 

 alive showing pseudopodia. 



composed some of our thickest beds of 

 rock structure The fleshy part of the 

 animal is simply composed of jelly-like 

 protoplasm, with no separate parts, and 

 without a nucleus in the centre. They 

 are divided into two sub-classes : those 

 with the shells perforated with minute 

 holes (perforata), and those with the shells 

 not perforated (imperforata). The perforata 

 send out long filaments (pseudopodia) 

 through the openings to catch their prey, 

 and the imperforata send them out through 

 the only opening, at one end Some of 

 them have the power of bringing their 

 bodies to the outside and covering the 

 shell. The shells are built up of cells, 

 the animal building a new cell when the 

 old one gets too small. They are some- 

 times built in a straight line, the smallest 

 cell at one end, and the largest at the 

 other ; or they are built in a spiral, and 

 in various other forms. They live in 

 shallow seas, that is, not deeper than two 

 hundred fathoms ; and when they perish, 

 their shells, or skeletons, as they are 

 sometimes called, sink to the lowest parts 

 of the ocean and form vast beds or layers, 

 as are now in process of formation in the 

 bed of the Atlantic, These beds, in the 

 course of ages, become elevated above the 

 sea level, and, by pressure, become solid- 

 ified and form rock. In this way most of 

 the limestone and chalk has been formed, 

 so you will see that these little animals 

 play an important part in nature. Most 

 of those found at the present day are but 

 small ; but some which lived when the 



