TUBE-DWELLING ROTIFERS. 33 



hesioii thereto of foreign matter. When completed 

 it is cemented to a firm support, and is no part or 

 attachment of the bod^ of its maker. 



This grouping or association into colonies, both 

 of these and other organisms, is very suggestive. 

 The tendency is more or less developed in propor- 

 tion to the strength or weakness of the individual, 

 and the peculiarities of its environment. Some 

 forms of life there are of a much humbler character 

 than those now under consideration, which yet are 

 solitary in their habits ; it will, however, be found, 

 on close examination, that they are furnished with 

 some subtle means, both of offence and defence, 

 which is often more than a match for those of 

 much higher organisation in the struggle for ex- 

 istence. 



Confining our attention for the present to the 

 Limnias and its relatives, we find it very interesting 

 to observe the various methods adopted in these 

 associations. Thus the Conochilus shelters all its 

 members in one common protecting substance which 

 envelopes the whole family circle. The Limnias, 

 on the other hand, preserves its individuality, while 

 yet combining with its neighbours in grouping 

 D 



