THE EVOLUTIONARY CAREER 



313 



iv. The Spermatophytes. Now the dominant plants. This 

 type was the latest of all to appear. At present it is represented 

 by the Flowering Plants, which are certainly the most dominant 

 and ubiquitous of all forms of terrestrial life. 



V. The Protozoa. Except for such Protozoa, like the Radio- 



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S- 



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^ 





S> 



r 







Co 







C<) 





/.aMaj£2^*iS£&^^ 



r 



MolLiLsccu 







Echinodernis \ 



-An-ciertt \=. 



■ CephaLop o cLs 



— H ' ^~' ! 



^ 



ProtozocL \ ^^^^^\ P'rot o zoia 



Sponges i 

 CcelsntsroMx, \ 



Arthropcda 



Cystyd^s I Bla^ UdLs C^ ^ds ^^^'^'^^^?'^ 



mvs 



Fig. 42. — Approximate Periods of the Main Types of Animals. 



laria, which have skeletons capable of fossilization, we know little 

 of the past of these organisms. But there is little doubt that they 

 have been a widely distributed and ancient form of life. 



vi. The Sponges and Coelenterates. Ancient and persistent 

 forms of animals with few vicissitudes in their past history. 



vii. The Molluscs , including the Lamellibranchs, Gasteropods, 

 Cephalopods, Heteropods, etc. There have been Lamellibranchs 



