Editing Euglena (section)

===Early observations===
[[File:Mullers cercaria viridis detail.jpg|thumb|left|300px|''Cercaria viridis'' (= ''E. viridis'') from [[Otto Friedrich Müller|O.F. Müller]]'s ''Animalcula Infusoria''. 1786]]
Species of ''Euglena'' were among the first protists to be seen under the microscope. In 1674, in a letter to the Royal Society, the Dutch pioneer of microscopy [[Antonie van Leeuwenhoek]] wrote that he had collected water samples from an inland lake, in which he found "animalcules" that were "green in the middle, and before and behind white." Clifford Dobell regards it as "almost certain" that these were ''Euglena viridis'', whose "peculiar arrangement of chromatophores...gives the flagellate this appearance at low magnification."<ref>{{cite book |last=Dobell |first=Clifford |title=Antony van Leeuwenhoek and his 'Little Animals' |url=https://archive.org/details/antonyvanleeuwen00clif |url-access=registration |location=New York |publisher=Dover |orig-year=1932 |year=1960 |page=[https://archive.org/details/antonyvanleeuwen00clif/page/111 111] |isbn=978-0-486-60594-4}}</ref> Twenty-two years later, [[John Harris (writer)|John Harris]] published a brief series of "Microscopical Observations" reporting that he had examined "a small Drop of the Green Surface of some Puddle-Water" and found it to be "altogether composed of Animals of several Shapes and Magnitudes." Among them, were "oval creatures whose middle part was of a Grass Green, but each end Clear and Transparent," which "would contract and dilate themselves, tumble over and over many times together, and then shoot away like Fish."<ref>{{cite journal |bibcode=1695RSPT...19..254H |jstor=102304 |doi=10.1098/rstl.1695.0036 |url=https://archive.org/details/philtrans01804684 |title=Some Microscopical Observations of Vast Numbers of Animalcula Seen in Water by John Harris, M. A. Rector of Winchelsea in Sussex, and F. R. S |year=1695 |last1=Harris |first1=J. |journal=Philosophical Transactions of the Royal Society of London |volume=19 |issue=215–235 |pages=254–9|doi-access=free }}</ref>

In 1786, [[Otto Friedrich Müller|O.F. Müller]] gave a more complete description of the organism, which he named ''Cercaria viridis'', noting its distinctive color and changeable body shape. Müller also provided a series of illustrations, accurately depicting the undulating, contractile movements ([[metaboly]]) of the cell body.<ref>{{cite book |url=https://archive.org/details/animalculainfuso00ml |last1=Müller |first1=Otto Frederik |last2=Fabricius |first2=Otto |title=Animalcula Infusoria, Fluvia Tilia et Marina |year=1786 |publisher=Hauniae, Typis N. Mölleri |pages=126, 473}}</ref> In 1830, [[Christian Gottfried Ehrenberg|C. G. Ehrenberg]] renamed Müller's ''Cercaria'' ''Euglena viridis'', and placed it, in keeping with the short-lived system of classification he invented, among the Polygastrica in the family Astasiaea: multi-stomached creatures with no alimentary canal, variable body shape but no pseudopods or lorica.<ref>[https://www.biodiversitylibrary.org/bibliography/2077#/summary Ehrenberg, C. Organisation, Systematik und geographisches Verhältnifs der Infusionsthierchen. Vol. II. Berlin, 1830. pp 58-9]</ref><ref>{{cite book |url=https://archive.org/details/historyofinfusor00pritrich |last=Pritchard |first=Andrew |title=A history of Infusoria, living and fossil: arranged according to 'Die Infusionsthierchen' of C.G. Ehrenberg |publisher=Whittaker |location=London |year=1845 |page=86 |hdl=2027/uc2.ark:/13960/t5fb4z64c}}</ref> By making use of the newly invented achromatic microscope,<ref>{{cite journal|journal=Notes and Queries|date=July–December 1855|volume=12|issue=13|pages=459|url=https://books.google.com/books?id=gwAjAQAAIAAJ&q=Notes+and+queries+ehrenberg+microscope&pg=PA459|title=Notes and Queries}}</ref> Ehrenberg was able to see ''Euglena'''s eyespot, which he correctly identified as a "rudimentary eye" (although he reasoned, wrongly, that this meant the creature also had a nervous system).  This feature was incorporated into Ehrenberg's name for the new genus, constructed from the Greek roots "eu-" (well, good) and glēnē (eyeball, socket of joint).<ref>{{cite encyclopedia |url = http://www.merriam-webster.com/dictionary/euglena |title = Merriam-Webster online dictionary |encyclopedia = Encyclopædia Britannica |access-date= 6 July 2005 }}</ref>

[[File:Dujardin euglena.jpg|thumb|200px|''Euglena'' from [[Félix Dujardin]]'s ''Histoire Naturelle des Zoophytes'', 1841]]

Ehrenberg did not notice ''Euglena''{{'}}s flagella, however. The first to publish a record of this feature was [[Félix Dujardin]], who added "filament flagelliforme" to the descriptive criteria of the genus in 1841.<ref>{{cite book |url=https://archive.org/details/histoirenaturell00duja |last1=Dujardin |first1=Félix |title=Histoire Naturelle des Zoophytes. Infusoires, comprenant la Physiologie et la Classification de ces Animaux, et la Manière de les Étudier a l'aide du Microscope |location=Paris |year=1841 |page=358}}</ref> Subsequently, the class Flagellata (Cohn, 1853) was created for creatures, like ''Euglena'', possessing one or more flagella. While "Flagellata" has fallen from use as a taxon, the notion of using flagella as a phylogenetic criterion remains vigorous.<ref>{{cite journal |doi=10.1078/143446103322454112 |title=Phylogeny and Classification of Phylum Cercozoa (Protozoa) |year=2003 |last1=Cavalier-Smith |first1=Thomas |last2=Chao |first2=Ema E.-Y. |s2cid=26079642 |journal=Protist |volume=154 |issue=3–4 |pages=341–58 |pmid=14658494}}</ref>