THE PROTISTA. 47 



must be connected at their lowest root, and likewise the 

 three or six main classes, or phyla, of the vegetable kingdom 

 must be traced to a common and most ancient original form. 

 How the connection of these tribes is to be conceived I shall 

 explain in the succeeding chapters. But before proceeding to 

 this, we must occupy ourselves with a very remarkable group 

 of organisms, which cannot without artificial constraint be 

 assigned either to the pedigree of the vegetable or to that of 

 the animal kingdom. These interesting and important 

 organisms are the primary creatures, or Protista. 



All organisms which we comprise under the name of 

 Protista show in their external form, in their inner struc- 

 ture, and in all their vital phenomena, such a remarkable 

 mixture of animal and vegetable properties, that they cannot 

 with perfect justice be assigned either to the animal or to 

 the vegetable kingdom ; and for more than twenty years an 

 endless and fruitless dispute has been carried on as to 

 whether they are to be assigned to this or that kingdom. 

 Most of the Protista are so small that they can scarcely, if 

 at all, be perceived with the naked eye. Hence the ma- 

 jority of them have only become known during the last 

 fifty years, since by the help of the improved and general 

 use of the microscope these minute organisms have been 

 more frequently observed and more accurately examined. 

 However, no sooner were they better known than endless 

 disputes arose about their real nature and their position in 

 the natural system of organisms. Many of these doubtful 

 primary creatures botanists defined as animals, and zoolo- 

 gists as plants ; neither of the two would own them. Others, 

 again, were declared by botanists to be plants, and by 

 zoologists to be animals : each claimed them. These contra- 



