ECHINELLEA. 



77 



They may be seen of various forms, some single, 

 others in groups ; some long and narrow, others 

 wedge-shaped, and occasionally they grow one 

 on the other. The individuals of one genus, 



4 



Gomphonema, form quite a little tree : each one 

 is wedge-shaped, and at certain periods becomes 

 detached, and creeps about, but it is not known 

 whether it forms another stalk ; it is found 

 attached to Lemna. Those of the genus EcMnetta 

 form a cluster like a fan, and this is caused by 

 the body dividing, but not the stalk, so that the 

 individuals, being wedge-shaped, as they lie side 

 by side, have a fan-like form. These are prin- 

 cipally found in the sea, attached to sea-weeds 

 and mollusca ; but two are found in fresh water. 

 The fourth section consists of curious little 



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