380 ORDER FLAGELLATA-EUSTOMATA. 



closely correspond with those of Astasia that the two have been usually included in 

 the same family. By Ehrenberg, indeed, the presence or absence of the so-called 

 coloured eye-speck was regarded as representing the only distinctive feature, the 

 natural sequence to such an artificial distinction being that many forms have been 

 referred by him to the genus Astasia which properly belong to the one now under 

 consideration. Dujardin was the first to point out the unreliable character of 

 Ehrenberg's proposed diagnosis, substituting for it the distinctions here maintained, 

 afforded by the coloured or transparent consistence of the endoplasm. This last- 

 named characteristic may still be adopted as furnishing a safe and speedy means of 

 distinguishing between the representatives of the two respective genera, although, as 

 will be presently shown, much more important structural differences exist. The 

 colouring matter of Euglena most usually green and apparently partaking of the 

 nature of chlorophyll which invariably, under normal conditions, enters to a greater 

 or less extent into the composition of the endoplasmic layer of the various species, 

 is, as already intimated in the account given of the genus Astasia, not scattered in 

 an irregular granular manner, as in numerous other infusorial forms, denoting by 

 such a distribution its foreign nature and temporary lodgment only, but permeates 

 its substance so completely as to be inseparable from it under the highest magnify- 

 ing power, and remaining as intimately amalgamated with it when, as described 

 later on, it breaks up within the integument into germinal masses. In this manner 

 the endoplasm of Euglena is, as it were, indeed, more or less completely stained 

 with the characteristic hue peculiar to the species. 



The possession by Euglena of a distinct oral aperture, and its capacity, of incept- 

 ing solid particles of ^food through this orifice, have not up to a recent date been 

 clearly demonstrated. Stein, however,* in the year 1867, went so far as to attribute 

 the office of such a structure to the notch-like anterior cleft of Amblyophis, and which 

 he described as being followed by a distinct pharyngeal tract ; a similar interpretation 

 was also arrived at by him with reference to the smaller anterior notch of Euglena, 

 though in no instance was the passage of food-particles directly determined. Still 

 later,t this authority has represented a tubular oral aperture as pertaining to all of 

 the members of this family group as here comprised. The apparent absence of a 

 distinct oral apparatus and ingestive capacity, taken together with the green hue of 

 the body-plasma, previously induced most modern authorities, including Mr. Carter, 

 to deny to the representatives of Euglena and its allies the rank of animal or- 

 ganisms, they referring them rather to the division of the Protophyta or lower 

 unicellular plants. The present author's views, to within a comparatively recent 

 date, harmonized with this decision, but a still later and more exhaustive examina- 

 tion of the type form of the genus, E. viridis, made in April 1877, has resulted in 

 the adoption of an entirely opposite opinion. Keeping animalcules of this species 

 for a prolonged interval in water with finely pulverized carmine, and submitting 

 them to a magnification of 800 diameters and upwards, the passage into their 

 bodies at the anterior extremity of exceedingly fine particles of this pigment was 

 repeatedly observed, as also the accumulation, in various parts of the body-substance, 

 of small globular aggregations of the particles ingested. Hitherto this anterior 

 region in Euglena has been represented as exhibiting a bilabiate aspect, and the 

 flagellum as a thread-like extension of the upper of the two lip-like prominences. 

 With the aid of the high magnifying power employed on this occasion, it was, how- 

 ever, clearly shown that the inner surfaces of these lip-like prominences actually 

 represented the upper and lower boundary walls of a conical or infundibular excava- 

 tion or vestibulum, the innermost recess of which fulfils the office of an oral 

 aperture by permitting the free passage of exceedingly minute food-particles. This 

 infundibular cleft, the walls of which are so thin and transparent as to require 

 the aid "of the highest powers of the microscope for their satisfactory delineation, 

 are at once suggestive of the infundibular, collar-like, pre-oral expansion of the 

 Choanophorous order of the Flagellata Codosiga, Salpingceca, &c., and may not 



' Infusionsthiere,' Abth. ii., 1867. t Ibid., Abth. iii., 1878. 



