THE RAY-STREAMERS. 63 
a snail, from the mouth of which a bundle of plasmic 
threads issues. In contrast to these single-chambered forms 
(Monothalamia), the many-chambered forms (Polythal- 
amia)—to which the great majority of the Acyttaria 
belong—possess a house, which is composed in an artistic 
manner of numerous chambers. These chambers sometimes 
le in a row one behind the other, sometimes in concentric 
circles or spirals, in the form of a ring round a central point, 
and then frequently one above another in many tiers, like the 
boxes of an amphitheatre. This formation, for example, is 
found in the nummulites, whose calcareous shells, of the size 
of a lentil, have accumulated to the number of millions, and 
form whole mountains on the shores of the Mediterranean. 
The stones of which some of the Egyptian pyramids are 
built consist of such nummulitic limestone. In most cases 
the chambers of the shelis of the Polythalamia are wound 
round one another in a spiral line. The chambers are con- 
nected with one another by passages and doors, like rooms 
of a large palace, and are generally open towards the outside 
by numerous little windows, out of which the plasmic body 
can stream or strain forth its little pseudo-feet, or rays of 
slime, which are always changing form. But in spite of the 
exceedingly complicated and elegant structure of this cal- 
careous labyrinth, in spite of the endless variety in the 
structure and the decoration of its numerous chambers, and 
in spite of the regularity and elegance of their execution, 
the whole of this artistic palace is found to be the sccreted 
product of a perfectly formless, slimy mass, devoid of any 
component parts! Verily, if the whole of the recent 
anatomy of animal and vegetable textures did not support 
our theory of plastids, if all its important results did not 
