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MANUAL OF ELEMENTARY ZOOLOGY 



a length of J mm. The front end is blunt and bears a flagellum 

 rooted at the base of a funnel-shaped pit, which 

 Haemafo' 1 " 1 is known as the "gullet" but probably never used 

 coocus. " as sucr >- There is a thin, horny cuticle, a distinct 



ectosarc, and a central, spherical nucleus. Arranged 

 in bands, radiating from the nucleus, lie a number of oval, green 

 bodies known as chloroplasts, which 

 consist of dense protoplasm containing 

 chlorophyll. Similar bodies are found in 

 green plants. Paramylum granules are 

 present, more numerous in sunlight. 

 Waves of contraction like those of Mono- 

 cystis pass along the body (Fig. 392), but 

 there are no myonemes. The excretory 

 system is complicated, consisting of a 

 reservoir opening into the gullet, a con- 

 tractile vacuole which discharges at in- 

 tervals into the reservoir, and a numbei 

 of accessory vacuoles which surround the 

 main vacuole and re-form it. A red pig- 

 ment spot or stigma lies against the fronl 

 side of the reservoir and is said to enable 

 the animal to appreciate the amount o: 

 light in its surroundings. Reproductior 

 is by binary fission, beginning at the fronl 

 end, the nucleus undergoing a peculiai 

 mitosis. It may take place in free in 

 dividuals after the loss of the flagellum, 

 or in a gelatinous cyst, within which il 

 may be repeated several times. A fonr 

 of conjugation, with amoeboid gametes, 

 has been reported in another species 

 Euglena. The nutrition of Euglena h 

 normally holophytic, but the water mus 

 contain a little albuminoid matter. I 

 the solution be rich in dissolved organic 

 matter, the chloroplasts grow pale anc 

 shrink. In the dark this takes placi 

 with a lower percentage of organii 

 matter, but in the absence of sucl 

 matter the creature remains green evei 

 in the dark. Thus Euglena is holophytii 

 and saprophytic. If it used its gullet fo: 

 taking food it would combine all threi 

 forms of nutrition. It will be seen tha 

 in certain respects Euglena resembles Polytoma. Polytoma, however 

 has nearer green relations, such as Hamatococcus (Fig. 393), and it i 

 interesting in this connection to recall that it is itself unlike mos 

 animals in forming starch. Zoochlorella (p. 167) has a flagellate stage 

 In fact, the position of a large number of Flagellata is doubtful a 

 between the animal and vegetable kingdoms. 



Fig. 391. — Euglena viridis, 

 highly magnified. 



a.v., Accessory contractile vac- 

 uoles ; c.v., main contractile 

 vacuole ; chp. t chromato- 

 phores ; cu., cuticle ; e.s., eye- 

 spot ; ic, ectoplasm; J?., 

 flagellum; g. t gullet; nu., 

 nucleus ; /.£"., paramylum 

 granules ; res. , reservoir. 



