MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 237 
but are continually varying in consequence of both intrinsic and 
extrinsic influences. The body in most cases is a mere fragment 
of naked protoplasm, with no differentiated covering, and with 
hardly, if any, indications of a differentiation of ectosarc and 
endosare. Owing to this and to their minute size, it is almost 
impossible to determine with any certainty many points regarding 
it when in a state of full activity. Nearly all reagents almost 
immediately produce destructive changes, leading on rapidly to 
disintegration and disappearance, and even slight changes in the 
medium, such as depression of temperature or dilution with 
water, are sufficient to arrest activity and induce disintegration. 
When in full activity they present a more or less fusiform or 
pear-shaped outline (Plate XVIII, fig.18). The size varies so 
- greatly, according to the nature of the medium and to the rate 
at which processes of multiplication by division occur, that it is 
useless to attempt any very precise statement regarding it. In 
three cases in which special notes of measurements were taken, 
the results were as follows: 
9°2 pw. 
It is almost as difficult to make any definite statement as to 
the number of flagella which is to be regarded as normal, as it 
appears to vary from one to three, or even four, in some cases. 
In such an undifferentiated organism the flagella differ little from 
pseudopodia, and their formation and retraction may frequently 
be observed in some of the more sluggish states of the body 
when movement is comparatively slow. This being the case, it 
is clear that any constancy in their numbers is hardly to be 
looked for. The posterior extremity of the body sometimes 
ends in a point, sometimes is more or less rounded, and fre- 
quently is provided with a caudal process, or trailing filament of 
very varying length and thickness. This appears to be con- 
nected with the method of nutrition proper to the organism, 
which is identical with that described by Cienkowski as prevail- 
ing among certain of the Monadine.? That portion of the 
body opposite to the site of the flagella, and therefore the pos- 
terior portion in reference to motion, is the point through which 
‘nutritive materials are absorbed into the body-mass. The pro- 
cess may sometimes be very clearly observed where the nutritive 
body, as is occasionally the case, consists of an amoeboid body 
or of a red blood-corpuscle. When a zoospore is about to be 
1 » = Micromillimétre = :001 mm. 
> “ Beitrage zur Kenntniss der Monaden,” ‘ Archiy fiir mikrosk. Ana- 
tomie,’ Bd. I, 1865, S. 203. 
