INTRODUCTION. 31 
such situations. The under-sides of the leaves of 
water-hles, the common Potamogeton, and other 
submerged plants, are likewise prolific of species. But 
for the finer forms of Hyulosphenia, the Nebelas, 
Heleoperas, etc., search must be made in Sphagnum- 
bogs and moorland pools. It is in such places that the 
rare Raphidiophrys elegans, Amphitrema (Ditrenca) 
flavum, and A. Wrightii were discovered by Mr. Archer, 
in Ireland, and there also the singular Chlamydoinyxa 
and the rarer Heliozoa may be looked for with success. 
In matters of habitat the Rhizopoda, like other 
creatures, have their preferences. It would be in vain, 
for example, to look for the beautiful Hyalosphenias, 
the Nebelas, or the rarer Reticularian species in the 
deep waters of a pool, or for Pelomyea amongst 
Sphagnum. Professor Penard has shown, by his inves- 
tigations at Geneva, that the deep waters of a lake ma 
contain new and unsuspected forms of life. The 
Amebe, Difflugie, and Arcelle seem indifferent to 
situation. Some of the rarer kinds may be gathered on 
dripping sandstone rocks among low forms of vegetation. 
Bogs, again, harbour the rarer species of the filose 
protoplasts. They are also the habitats of the naked 
Reticularians, Biomyxa, Gymnophrys, and Penardia, and 
also of Chlamydomyvra, which in its resting-state is 
parasitic on Sphagnum. The moss Dicranella cervicu- 
lata, which covers with a velvety-green mantle the 
sides of deep drains on peat-bogs, gives shelter to a 
great variety of forms, notably the delicate little 
Pamphagus hyalinus, as well as some of the smaller 
Huglyphe, Cyphoderia ampulla, Trinenva acinus, Assulina 
seninulum, ete. Nebela bursella is met with in associa- 
tion with these, but in an ill-developed state usually 
arising from insufficient moisture in summer. Micro- 
gromia occurs in colonies, mostly in shallow bog-pools, 
along with Pompholyzophrys, Acanthocistis, and Vai- 
pyrella lateritia, but not invariably so. We have met 
with it in sluggish streams, in masses of filamentous 
alge, and in ponds among the fohage of aquatic Hypi ; 
