BY G. I. PLAYP4IR. 117 



eml ; chluioplasts pale green, irregularly oval, disposed more towards the hinder 

 end; liagellum single; c.v. two, apical; and a yellow-hrown, wick-shaped, sub- 

 apical stigma. A stigma of this shape and colour is extremely rare among the 

 Eiif/leiiiiifae, though not uncommon in Chlamydomonas of the Volvocaceae. 



Genus E U g l e n a Ehrenberg. 

 EuGLENA viRiDis Ehr. (PI. iii., tig. 7). 



Of medium size; when young fusiform iu shape (cf. fig. 9), but with growth 

 tending to become cylindrical; blunt in front and rapidly attenuated behind 

 where it is drawn out into a minute tail. No flagellum, or only the useless stump 

 of one. Amylaceous granules irregular in shape and size, generally forming 

 a large central mass in front of and behind the nucleus. Membrane smooth but 

 very fine spiral striae can generally l)e detected with a high power lens on all 

 species of Euglen-a. A few minute digitate chloropla.sts are usually visible in 

 the hinder part of the cell, but the usual discoid chloropla-sts form with age. 

 prmcipally iu the central portion, leaving the ends hyaline. , From Daugeard's 

 description and figure (Reeherehes sur les Eugleniens, p. 43, fig. 1a, d) the young 

 lusiform specimens are characterised by a stellate bundle of digitate chloro- 

 jilasts radiating from the centre of the cell. The dimensions he assigns are long. 

 <)8 — 80, lat. 14 — 16^,. This is perhaps more nearly Ehrenberg's type. Thai 

 which I figure here is the older cylindrical form: long. c. 110, lat. 14^. 



This species develops in the globular vegetative cell in a manner peculiar 

 to itself. Both head and tail are turned in under the body, on the same side, 

 to form a ball. When the mucus in which this globular cell is involved gets 

 sufficiently thin for the creature to get free, it simply unrolls head and tail and 

 straightens itself out. 



Var. SANGUINEA (Ehr.). 



Euglena sanguinea Ehr. This red form is usually found in company with 

 the type, especially when, as often happens, the organisms form a powdery 

 crust on the surface or on the half-dry bed of a pool. It is probably due to 

 the action of sun and air. Under the microscope the colour will be seen to be 

 due to the gradual conversion of the chloroplasts into orange or brick-red 

 globules of haematochrome (lipochrome). This is known to take place in the 

 Protococcaceae also. 



Var. PURPUREA, n.var. 



A rarer and very striking form. The chloropliyll ha.s become converted 

 into a wine coloured substance disposed to all appearances in fine grains. 



Euglena sociabilis Daugeard. (PI. iii., figs. 8, 9). 



Very like the young form of Euglena viridis, but broader and more davate 

 in front. It may always tie recognised l)y the digitate chloroplasts regularly 

 disposed from front to back. Amylaceous granules irregular iu shape, arrange<l 

 in a mass before and behind the nucleus and below the chloroplasts. Membrane 

 smooth, finely striate spirally and obliquely from left to right. With or witliout 

 a flagellum. 



Long. 92—95, lat. 21—28^. Lismore (254, 293, 308, 316, 327). 



Cf. Daugeard, op. cit., p. 86, fig. 15; for dimensions he gives 85 X 25^. 

 This species almost certainly develops into the cylindrical form of Euglena 

 viridis mentioned above. It is really the young aquatic form, while E. viridis 



