THE EAY-STREAMERS. 63 



a snail, from the mouth of which a bundle of plasmic 

 threads issues. In contrast to these single-chamhered forms 

 (Monothalamia), the Tnany-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 

 lie 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 shells 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 secreted 

 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 



