§<§> 4, 5. INFUSORIA AND PJIIZOPODA. 21 



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

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

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

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

 place to place bj 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 Bacillareae and Diatomacefe, this question has another aspect. 

 Many of these oi-ganisms 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 Diatomaceas, 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 Ehrenberg/'^ 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 Rhizopoda, on the other hand, although 

 ec^ually 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 ihe 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 Ehrenberg, into two 



* As an example, may be mentioned the various Also, Kiitzing, XJeber die Vervvandlunj der 



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



question of the animal or vegetable nature of the 1844. 



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



after the moat careful studies, is still undecided, inter regnum animale et vegetabile constiluendis, 



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



in Nov. Act. Acad. Leop. Carol, vol. XX. part ii. confusi.jn between the two kingdoms does not e.xist. 



p. 18. 6 Abliandlungen der Akademie der Wissen- 



6 See linger, Die Pflanze im Momente der schalteu zu Berlin, 1836, p. 134, Taf- I. fig. 19, and 



Thierwerduiig. Wien. 1843. lS3y, p. 1U2, Taf. IV. fig. 5. 



