316 



EVENINGS AT THE MICROSCOPE. 



sions ; and therefore I will merely say here that each one 

 of these tiny vesicles carries a barbed and poisoned arrow, 

 which can be shot forth at the pleasure of the animal with 

 great force, and to an amazing length ; that hundreds are 

 usually shot together ; and that this is the provision which 

 the All-wise God has given to 

 these apparently helpless animals 

 for securing and subduing their 

 prey. 



There is, however, another 

 organ still more conspicuous in 

 our little Sarsia, of which I have 

 not yet spoken. As the whole 

 animal has the most absolute 

 transparency, we see that the 

 roof of the bell is much thicker 

 than the sides, and that it gradu- 

 ally thins oflf to the edge. The 

 interior surface is called the sub- 

 umbrella, and it carries within 

 its substance four slender tubes, 

 which, radiating from the centre 

 of the roof, proceed to the mar- 

 gin, where they communicate 

 with another similar canal which 

 runs round the circumference, 

 sending oflf branches into the 

 tentacles. This is the circulatory 

 system; and you may see, with 

 the magnifying power which you 



are at present using, that a clear fluid is moving rapidly 

 within all these canals, carrying minute granules ; not 

 with an even forward current, but with an irregular jerk- 

 ing movement, as if several conflicting eddies were in the 

 stream. Yet we discern that, on the whole, the granules 

 are moved forward ; passing from the centre of radiation 



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