GENUS EUGLENA. 379 



escape from the cysts in a form identical with that of the parent, but of smaller 

 size. Not unfrequently, as shown at PI. XX. Fig. 22, two or three Colpodella fasten 

 themselves simultaneously to a single Chlamydomonas, and perforating its body- 

 wall, rapidly reduce it to an empty shell. No instance of the coalescence or fusion 

 of two or more individual zooids has as yet been recorded, but in all probability 

 occasionally takes place. 



Fam. III. EUGLENTD-ffi, Stein. 



Animalcules free-swimming or sedentary, naked or loricate, solitary or 

 united in social colonies ; flagellum single, terminal ; oral aperture distinct ; 

 endoplasm usually coloured brilliant green, more rarely red, through the 

 assimilation of chlorophyllaceous substances, often enclosing several highly 

 refracted corpuscles of an apparently starch-like or amylaceous nature ; one 

 or more brightly coloured eye-like pigment-specks frequently developed at 

 the anterior extremity; contractile vesicle and endoplast conspicuous, the 

 former usually located close to the anterior border. Multiplying by longi- 

 tudinal and transverse fission, by the subdivision of the entire body- 

 substance into sporular elements, and by the development of independent 

 germinal bodies out of the substance of the endoplast. 



The members of this highly characteristic and very natural family group are 

 readily recognized in connection with the brilliant coloration the prevailing hue 

 being green of the endoplasmic elements, which under normal conditions more 

 or less conspicuously distinguishes every one of the considerable number of 

 generic and specific types as herewith comprised. The common occurrence within 

 the body-substance of variously shaped corpuscles of considerable size and of an 

 apparent amylaceous or starch-like nature, as also the endogenous mode of repro- 

 duction, manifested by the enlargement and subdivision of the central endoplast 

 or nucleus, yield supplementary distinctive features of importance. With respect to 

 the amylaceous corpuscles, it is worthy of remark that in the case of those of elongate 

 rectangular contour developed in Euglena deses, Dujardin has attributed to them the 

 nature of crystals of sulphate of lime. 



GENUS I. EUGLENA, Ehrenberg. 



Animalcules free-swimming, more or less fusiform or elongate, exceed- 

 ingly flexible and changeable in shape ; bounded by an elastic and highly 

 contractile cuticulum, terminating posteriorly in a more or less deve- 

 loped tail-like prolongation ; endoplasm usually tinged bright green or 

 red through the assimilation of chlorophyll or other colouring matter ; 

 flagellum single, slender and flexible throughout, issuing from an anterior 

 funicular, notch-like excavation, at the bottom of which a minute oral 

 aperture is situated ; contractile vesicle and endoplast conspicuous ; one or 

 more distinct eye-like pigment-spots usually present at the anterior extre- 

 mity. Inhabiting fresh, stagnant, and brackish waters ; solitary, or occurring 

 in such numbers on the surface of the water as to impart to it a highly 

 characteristic feature, even as seen with the unaided vision. Increasing by 

 longitudinal fission, and by the production of germs through the subdivision 

 of the endoplast or of the entire mass of the internal parenchyma. 



In their general contour and extreme flexibility, which permits them at wiU to 

 assume the most varied and protean shapes, the members of the genus Euglena so 



