XIX. 



SEA-URCHINS are frequently taken in dredging. 

 Several common species, usually of a small size, are 

 often found among the rocks situated between tide 

 marks. 



Into the aquarium no specimens larger than from 

 one to two inches in diameter should be introduced, 

 and even these require to be closely watched, for if 

 afflicted with a fatal illness, I know of no animal 

 whose remains sooner taint the water. Almost be- 

 fore life is extinct, the Urchin throws out a light- 

 coloured nauseous fluid, that speedily poisons the sur- 

 rounding water, and, of course, causes the destruction 

 of any inhabitants of the tank who may neither 

 have the sense nor opportunity to inhale copious 

 draughts of fresh air. As a rule, if the suckers are 

 motionless, or if on touching the animal it is 

 found not to be adherent to any object, transfer it 

 at once to your ' infirmary ' for further observa- 

 tion. 



I have always found small specimens to be much 

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