Protozoa. 19 



to be found minute calcareous shells of varying forms 

 (figs. 7, 8), ranging from -^th to -^th of an inch in 

 diameter. Each shell consists of many separate cham- 

 bers, arranged either one after another in a straight 

 line or in a single or double spiral, or even grouped in 

 more complex fashions. Each chamber is separated 

 from its neighbours by a* partition which is pierced 

 with one or many holes whereby the several chambers 

 communicate with each other. The shell-substance 

 is either white and porcelain-like, or glass-like and more 

 brittle, and pierced not only in the partitions but over 

 its whole surface by numerous holes. On account of 

 these perforations these little shells are called Forami- 

 nifera (hole bearing). 



The animals which build these wonderful houses 

 are exceedingly simple in their structure. The interior 

 of each chamber in a fresh state is filled with proto- 

 plasm which is jelly-like, highly contractile on being 

 irritated, and not only extends through the holes in 

 the shelly wall but coats the outside of the shell with 

 a glairy external living layer. This layer has no defi- 

 nite uniformity of outline, but is constantly changing 

 its shape by sending into the surrounding water 

 radiating protoplasmic processes which are incon- 

 stant, rapidly retracted, disappearing by being taken 

 into the homogeneous matter of the animal's body, 

 and coalescing when they touch each other. To these 

 the name psetidopodia (false feet) has been given. 



These little creatures live on any minute organic 

 particles with which they come in contact, and their 

 mode of feeding is simple ; when the ray-like pseudo- 

 podia touch ft particle of which they seem to approve 



