216 FUNCTIONS AND INSTINCTS. 



and even nervous nodules or ganglions, and also 

 several ovaries. 



In mild calm weather, when the sun shines, 

 they may be seen in places, where the water is 

 not very deep, expanding their many-coloured 

 flowers at the surface of the waters but upon 

 the slightest indication of danger, the flowers 

 suddenly disappear, the animal contracts itself 

 and wears the aspect of a mass of flesh. They 

 as it were, vomit up their young, or the germes 

 formed in the ovaries : but they sometimes force 

 their way out from other parts. When inclined 

 to change their station they glide upon their 

 base, or completely detaching themselves, com- 

 mit themselves to the guidance of the waves. 

 Reaumur observed them use their tentacles like 

 the Cephalopoda, for locomotion. They fix 

 themselves with so much force, that they cannot 

 be detached without crushing them. 



It is not wonderful that so many of the lower 

 aquatic animals should have been mistaken for 

 plants, when they so exactly represent their 

 forms, their roots, their branches and twigs, 

 their leaves and their flowers but besides the 

 irritability of the animal substance, which 

 however is partially exhibited by some plants ; 

 there is another character which seems, as a 

 strong line of demarcation, to be drawn between 

 them, and to which I have before adverted; 1 



1 See above, p. 139. 



