ZOOPHYTES. 71 



our readers by adopting the following simple arrangement of these 

 animals into 



I. PROTOZOA, including the Spongiadse, Infusoria, and Fora- 

 minifera. 



II. POLYPIFERA, including the Hydrse, Sertularia, and Penna- 

 tularise. 



III. ECHINODERMATA, or Sea-urchins and Star-fishes. 



Our space will prevent our doing more than presenting to the 

 reader in succession the most characteristic types of each of these 

 groups. 



I. THE PEOTOZOA. 



The Protozoares represent animal life reduced to its most simple 

 expression. They are organized atoms, mere animated and moving 

 points, living sparks. As they are the simplest forms of animal life 

 as regards their structure, so also they are the smallest. Their micro- 

 scopic dimensions hide them from our view. The discovery of the 

 microscope was a necessary step to our becoming acquainted with 

 these beings, whose existence was ignored by the ancient world, and only 

 revealed in the seventeenth century by the discovery of the microscope. 

 When armed with this marvellous instrument, applied to examine 

 the various liquid mediums as when Leuwenhoek, for example, ap- 

 plied the magnifying glass to the inspection of stagnant water, with 

 its infusions of macerated vegetable and animal substances when he 

 scrutinized a drop of water borrowed from the ocean, from rivers, or 

 from lakes, he discovered there a new world a world which will be 

 unveiled in these pages. 



Some modern writers believe that the Protozoa is a mere cellular 

 organism, that being the principle and end of organization, such as 

 we find it in the cellular vegetable. According to this hypothesis, the 

 Protozoares would be the cellulars of the animal kingdom, as the Algae 

 and Mushrooms are of the vegetable world. This idea is so far 

 wrong, that it has been founded upon the empire of pure theory. 

 " In reality," says Paul Gervais and Yan Beneden, " the animals to 

 which we extend it very rarely resemble elementary cellulars." The 

 tissue of which the bodies of the Protozoa are composed is habitually 

 destitute of cellular structure. They are formed of a sort of animated 

 jelly, amorphous and diaphanous, and have received from Dujardin 

 the name of Sarcoda, or soft-fleshed animals. 



