382 ORDER FLAGELLA TA-EUSTOMA TA. 



Euglena viridis. The existence of the contractile vesicle in this species, and its 

 rhythmical though slow pulsations, were distinctly authenticated on repeated occa- 

 sions. In various instances there appeared to be two of these organs situated close 

 to one another near the anterior eye-like pigment-spot In demonstration of the 

 unreliability of the characters afforded by the last-named structure, Dujardin figures 

 an example in which no less than three of these coloured bodies are present, while 

 instances not unfrequently occur in which it is altogether absent. 



Stein, in his recently published work,* has given very copious illustrations of 

 this cosmopolitan species. From them are here reproduced his delineations of 

 a mode of reproduction that has not been previously recorded. This, as shown at 

 Figs. 39-41 of PL XX., is brought about by the abnormal growth and enlargement 

 of the endoplast, which next breaks up into innumerable spore-like bodies that 

 are finally liberated during the life of the animalcule as minute monadiform germs. 

 A similar process of reproduction is likewise attributed by this same authority 

 to the genus Trachelomonas. Encysted conditions resulting in the subdivision of 

 the entire body-mass into sporular bodies, as delineated by Stein, are reproduced at 

 Figs. 44-48, while simple fission, as it occurs in the temporarily encysted state, is 

 represented at Fig. 43. Fission during the motile life of this animalcule takes place 

 in a longitudinal direction. 



An interesting local variety of Euglena viridis has been recently described by 

 Mr. M. H. Robson, of Newcastle-upon-Tyne, in ' Science Gossip ' for October 1879, 

 in which the distal extremity of the flagellum presents an inflated knob-like aspect, 

 as shown at PI. XX. Fig. 29. Possibly such modification of this important organ 

 represents a phase preliminary to its entire withdrawal, and antecedent to the 

 entrance of the animalcule upon the encysted or resting state. 



Euglena spirogyra, Ehr. PL. XX. FIGS. 27 AND 28. 



Body elongate, sub-cylindrical, seven or eight times as long as broad when 

 extended ; slightly truncate anteriorly, the posterior extremity produced as 

 a transparent, ensiform, tail-like prolongation ; cuticular surface ornamented 

 with even closely approximated oblique rows of minute bead-like elevations ; 

 colour bright green, yellow, or brown ; endoplasm usually containing two 

 large ovate or elliptical amylaceous bodies, between which the ovate or 

 subspheroidal endoplast is located ; contractile vesicle situated at the 

 anterior extremity immediately behind the scarlet eye-like pigment-spot. 

 Length 1-240" to 1-120". HAB. Fresh water, solitary. 



According to Mr. Carter, the obliquely striate aspect of this and other species 

 of Euglena is occasioned by the presence beneath the cuticle of a layer of pointed 

 sigmoid fibrillae. The examination of numerous living examples of this type by 

 the present author, with the aid of a magnifying power of 800 diameters, has, 

 however, failed to reveal any such complex structure, though, on the other hand, 

 the entire surface of the cuticle was shown to be traversed by oblique rows of 

 closely approximated bead-like prominences ; the peripheral margin of the body 

 presented at the same time a finely crenulate aspect, demonstrating that the bead- 

 like appearance was a structural reality, and not a mere optical appearance. A 

 similar beaded pattern of the cuticular layer, though of a more open character, is 

 furthermore characteristic of the figures of this species as given by Stein. In 

 addition to the central nucleus or endoplast, two large obliquely disposed elliptical 

 or subcylindrical amylaceous corpuscles, situated, the one a little in front of, and the 

 other shortly behind, the centre of the body, as shown at PL XX. Fig. 27 a a, 

 were usually observed. The contractile vesicle, as in E. viridis, is located imme- 

 diately to the rear of the eye-like pigment spot. 



' Infusionsthiere,' Abth. iii., 1878. 



