JELLY-FISHES. 3G3 



gelatinous flesh, in wliicli are imbedded a score or two 

 of tinj oval vesicles, without any very obvious ar- 

 rangement; but for the most part so placed that the 

 more pointed end of each is directed toward the cir- 

 cumference of the thickenins;. The intermediate slen- 

 der portions of the tentacle — the thread on which the 

 beads are strung — is quite destitute of these vesicles. 



These little bodies are called cnidcB, and, in the 

 whole of this class of animals, and also in that of Zoo- 

 phj'tes, they play an important part in the economy of 

 the creature. I shall probably take occasion to exhibit 

 them to you under conditions more favourable than are 

 presented here, viz. in the Sea-Anemones, where they 

 attain far greater dimensions ; 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-Avise God has given to these apparently 

 helpless animals for securing and subduing their prey. 



There is, however, another organ still more conspic- 

 uous in our little Sarsia. of which I have not vet 

 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 gradually thins oif to 

 the edge. The interior surface is called the sub-um- 

 brella, and it carries within its substance four slender 

 tubes, which, radiating from the centre of the roof, 

 proceed to the margin, where they communicate with 

 another similar canal which runs round the circumfer- 

 ence, sending off branches into the tentacles. This is the 

 circulatory system ; and you may see, with the magni- 



