FRESH-WATER RHIZOPODS 145 



outer covering of the smallest specimens consist of 

 chitinoid membrane, a substance closely allied to the 

 hard covering of insects, and that the larger forms were 

 able to appropriate extremely small particles of quartz 

 sand and other materials, with which they covered 

 themselves in most artistic fashions. Notwithstand- 

 ing that both these families of Difflugia occupy the 

 same sphagnous swamps, their coverings were quite 

 different. They can be found everywhere in the ooze 

 of ponds, bogs, and ditches. Their life-history is 

 unknown, so that here is an opportunity at hand for 

 some patient student of Nature to study their cycle of 

 life, their habits and their usefulness in the ereat 



o 



range of natural wonders. All that is known of 

 these remarkable forms of life may be summed up in 

 a few words. Many of their different subdivisions are 

 known, and points of difference in their colour and 

 shapes are familiar to students of this department of 

 microscopic life their measurements, although ex- 

 tremely minute, are tabulated ; their habitat, kinds 

 of coverings, and a few of their peculiarities have 

 been studied by just a few naturalists, probably not 

 more than ten. Many more points in their history 

 must be made out before we can say we thoroughly 

 know the Difflugia. 



In the next illustration all the shells, with the ex- 

 ception of the last, are for the most part composed 

 of animal matter belonging to the creatures them- 

 selves, and hardened into special shapes, some of 

 which have ornaments in the way of plates arranged 



K 



