224 ERNST HAECKEL. 



soria), or (4) of an aggregate of simple, similar cells (poly- 

 cellular Gregarinae, Synamoeba), or, lastly (5), those where 

 the cells of the body may even be differentiated to a slight 

 extent, but which still form no germ-lamellae, and enclose 

 no true intestinal cavities. The individuality of the Protozoa 

 always remains fixed at a very low point ; that is, they either 

 form a morphon of the first order, a simple plastid (a cytode 

 or a cell), or they form, at most, a morphon of the second 

 order, an " organ " in a purely morphological sense, an 

 idorgan (see the doctrine of individuality in the * Biology of 

 the Calcareous Sponges,' p. 103, &c.). But the Protozoa 

 never raise themselves to the importance of a morphon of 

 the third or fourth order, a Person or a Stock (in the sense 

 defined in the passage quoted) . Just as a true intestine (the 

 first and oldest organ of the germ-lamellar a,nimals) is want- 

 ing in the Protozoa, so are absent also all the differentiated 

 systems or organs which we find in the former. The 

 Protozoa have no nervous system, muscular system, vascular 

 system, dermal system, &:c. They also want the differen- 

 tiated tissues. 



On the important grounds which I have fully developed 

 in the second volume of the ' General Morphology ' and in 

 my * Monograph of Monera,' it seems to be a real advantage, 

 especially towards the comprehension of general biology, to 

 separate a large portion of the so-called Protozoa from the 

 animal kingdom, and to relegate them to the neutral kingdom 

 of Protista, intermediate between the animal and vegetable 

 kingdoms. To this would belong part of the Monera, the 

 Ama?boida, and Flagellata, in addition to the Catallacta, the 

 Labyrinthulea, the Myxomyceta, and the entire class, so rich 

 in forms, of Rhizopoda, with all its different divisions ; 

 Acyttaria, Radiolaria, &c. All these Protista are to be re- 

 garded as independent organic stems or phyla, which do not 

 stand in any kind of genealogical connection with the animal 

 kingdom,and consequently do not belong to its natural system. 

 On the other hand, there are very simple organisms which 

 either belong to the actual stem-forms of the animal kingdom, 

 and form the true root of the animal genealogical tree, or 

 represent independent offshoots from that root, as well as 

 those very simple organisms which display an undoubtedly 

 animal character (as the Infusoria) , which are to be separated 

 from these neutral primary forms or Protista as true primary 

 animals or Protozoa. These Monera and Amcebcc should 

 be regarded as true primary animals, rejiresenting the 

 oldest stem-forms of the animal kingdom, and I have classed 

 these in the fourth edition of the Scho^jfungsgeschichte 



