^§ 4, 5. INFUSORIA AND RIIIZOPODA. 21 



often be seen the so-called organization of JLhrenherg's Monadina and 

 Volvocina. Until the fact that ciliated organs belong to both animals and 

 vegetables was decided, the real place of many low organisms had to 

 remain undetermined/''* However, notwithstanding their free motion from 

 place to place by means of cilia, the vegetable nature of many organisms 

 seemed clearly indicated by the rigid, non-contractile character of their 

 forms. It is from a misapprehension of the true nature of these facts, that 

 some modern naturalists have denied the existence of limits between the 

 two kingdoms. '^' 



With Bacillarese and Diatomaceae, this question has another aspect. 

 Many of these organisms have been taken for animals from their so-called 

 voluntary movements, which truly entirely want the character of volition. 

 In the movements of the rigid Diatomacege, for instance, the whole plant has 

 oscillatory motions like a magnetic needle, at the same time slightly 

 changing its place forward and backward. When small floating particles 

 come in contact with such an organism, they immediately assume the 

 same motion. This may be well observed with the Oscillatoria, There 

 are here, undoubtedly, no ciliary organs ; in fact, they could not, if pres- 

 ent, produce this kind of motion. According to ^Are^i^er^,'"* the Naviculae 

 can protrude ciliary locomotive organs through openings of their carapace; 

 but this has not been observed by other naturalists. 



§4. 



The Rhizopoda, whose internal structure is as yet imperfectly known, 

 are closely allied to the Infusoria. Like these last, their bodies are cellu- 

 lar, containing nuclear corpuscles, but no system of distinct organs. These 

 two classes of Protozoa differ, however, in their external form, and the 

 structure of their locomotive organs. The body of the Infusoria, notwith- 

 standing its contractility, has a definite form, and moves chiefly by means 

 of vibratile organs. That of the Hhizopoda, on the other hand, although 

 equally contractile, has no definite form ; their movements also are not 

 due to ciliated organs, but to a change of the form of the body by various 

 prolongations and digitations. 



§5. 



Owing to the present incomplete details upon the organization of these 

 animals, little can here be said about them ; and therefore, instead of 

 devoting to them a separate chapter, it will be proper to treat of them 

 with the Infusoria in general. 



As the division of the Polygastric Infusoria, by Ehrenherg, into two 



< As an example, may be mentioned the various Also, Kiitzing, TJeber die Verwandlung der 



and dissimilar opinions of naturalists upon the Infusorien in niedere Algenformen. Nordhausen, 



question of the animal or vegetable nature of the 1844. 



"red snow;" a question upon which Flntow, In an academic paper (Dissertatio de finibus 



after the most careful studies, is still undecided, inter regnum animale et vegetabile constituendis. 



See Flotow, " Ueber Haematococcus pluvialis, " Erlangae, 1844), I have attempted to show that this 



in Nov. Act. Acad. Leop. Carol, vol. XX. part ii. confusion between the two kingdoms does not exist, 



p. 18. 6 Abhandlungen der Akademie der Wissen- 



6 See Unger, Die Pflanze im Momente der Schäften zu Berlin, 1836, p. 134, Taf. I. flg. 19, and 



Thierwerdung. Wien. 1843. 1839, p. 102, Xaf. IV. flg. 5. 



