1885.] Infusoria from Fresh Water. 25 
become apparent to a trained eye, and even then only as infini- 
tesimal lines on the lateral borders of the extended bodies. No 
more careful adjustment of the objective, no more careful man- 
ipulation of the mirror is needed to study the markings of a 
diatom than is demanded by this little creature before its mark- 
ings impress the observer’s retina. In the figure (Fig. 8) they 
are represented by lines, fine it is true, but almost out of propor- 
tion to the elevations which Nature has placed on the living sur- 
face of the infusorial atomie, whose home was at the brink of 
that stupendous cataract of emerald and foam and spray- 
smoke, amid the eternal complaining of beaten rock and broken 
flood. 
The supporting pedicel is usually simply bifurcated at a point 
distant from its algal attachment about twice as far as are the fur- 
cations of the branches from the extremity of the main rachis. 
Sometimes the pedicel throws off three branches from its sum- 
mit, and more frequently four divisions. The prevailing form, 
however, is the dichotomous. Above the second series of bifur- 
cations the branches become of diverse: lengths, instances occur- 
ring in which the branchlet is twice as long as any other part. 
The length of the ultimate divisions, those immediately support- 
ing the zodids, seems quite constant, being usually about one- 
half as long as the extended body. The whole pedicel is stout 
and robust, and, is conspicuously marked by longitudinal strie. 
Its contractions are comparatively slow and few. There is none 
of that sudden coiling, as with the Vorticellz, when the expanded 
_ infusorian leaps back into quick contractions and momentary qui- 
escence that often startles the rapt observer. 
After the colony has been under observation for a prolonged 
period an action takes place that I have not seen recorded with 
any member of the genus, a movement recalling the contractile 
performances of the disconnected muscular threads of individual 
members of Carchesium. Two neighboring zodids fold together 
their ciliary apparatus, and their own private foot-stalks retract 
into coils without disturbing the general equanimity of the com- 
munity. This has been observed repeatedly, the retracted mus- 
cular thread being, in every instance, in apparent connection with 
that of the remainder of the pedicel. This thread, however, 
seems to be delicate. For no visible reason it soon separates into 
numerous scattered fragments within the sheath. In those in- 
