28 Lessons in Zoology. 



show beautifully in little circles around the spines. 



Covering the star-fish we see the brown skin, and look- 

 ing on the inside of the back of the separate rays, we 

 find the beams of the skeleton, like little bones imbed- 

 ded in the flesh, making an irregular net- work. 



Every one who haa seen a living atar-fisli, haa noticed the 

 differenoe between ita ronnded ontline in the water and ita flat- 

 tened appearance when thrown up ou the 

 beach. Thia ia becanae the akin o{ the 

 back ia paahed out into nnmerona tubea 

 like tin; glove-fingera (Fig. 3, d), bo thin 

 and delicate that they fill with water and 

 again allow it to ooze ont of them when 

 expoaed to the air. Theae tnbea, that 

 can aoarcely be aeen by the naked eye, 

 „ are really alao a rudimentary aort of 



gilla, for through their thin walla oxygen 

 paeaea from the water into the body of the atar-fiah. 



Lesson II. 



We now atndy the ander or month aide of the atar-fiah. Some of 

 the specimena will ahow the month aa a large oircnlar opening 

 with a membrane anrronnding it ; othera will have a brown maaa, 

 the dried atomach, filling the opening or protruding from it ; and 

 atill othera may have it nearly hidden by ten long spinea, two from 

 each ray, meeting over it like ao many teeth. 



The mouth with the long spines around it, the stomach 

 usually seen just inside it, and the brown suckers filling 

 the grooves in the rays (Fig. 4) first attract our attention. 

 The stomach can be protruded by means of muscles at- 

 tached to it. This is because our friend feeds on shell- 

 fish, working great havoc on the oyster and mussel beds. 

 It clasps an oyster with its rays, then turns out its stom- 

 ach, and proceeds to digest its victim at its leisure. A 

 star-fish will clean a shell in this way more perfectly 

 than it can be done by hand. 



