XIV. DIVISION OF LABOR. THE VARIOUS FORMS OF 



PLANTS AND ANIMALS 



Problems. — The development and forms of plants. 

 The development of a simple animal. 

 What is division of labor ? In what does it result ? 

 How to know the ehief chara^eters of some great animal 

 groups. 



Laboratory Suggestions 



A visit to a botanical garden or laboratory demonstration. — Some of the 

 forms of plant life. Review of essential facts in development of bean 

 or corn embryo. 



Demonstration. — Charts or models showing the development of a many- 

 celled animal from egg through gastrula stage. 



Demonstration. — Types which illustrate increasing complexity of body 

 form and division of labor. 



Museum trip. — To afford pupil a means of identification of examples 

 of principal phyla. This should be preceded by objective demonstration 

 work in school laboratory. 



Reproduction in Plants. — Although there are very many 

 plants and animals so small and so simple as to be composed of 

 but a single cell, by far the greater part of the animal and plant 

 world is made up of individuals which 

 are collections of cells living together. 



In a simple plant like the pond scum, 



, • ni i. r 11 • ^ J A cell of pond scum. How 



a strmg or filament of cells is formed ^.^^^ -^ ^^^^^ ^^ ^^^^ ^ i^^g 

 by a single cell dividing crosswise, the thread made up of cells ? 

 two cells formed each dividing into two 



more. Eventually a long thread of cells is thus formed. At times, 

 however, a cell is formed by the union of two cells, one from each 

 of two adjoining filaments of the plant. At length a hard coat 

 forms around this cell, which has now become a spore. The 

 fcough covering protects it from unfavorable changes in the sur- 



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