ANALYSIS OP HALL OP SHELLS. xix 



its connection by strong muscle witli the animal tested. 

 Look up in an encyclopaedia how the cartilaginous air vesi- 

 cles composing the egg float of the sea snail are secreted 

 and how attached. 



Chapter VI. — The dip net brings up marvels un- 

 dreamed of before ; the brine and mud become full of les- 

 sons ; hydroids, scalaria, stomapod, and Sajjphirina give 

 up their secrets. The sea bottom is shown by science to 

 be more than a fairyland. A dip net may be used in study 

 in either salt or fresh water. Read The Bottom of the 

 Sea, by T. Sourel. 



Chapter VII. — The Physalia or Portuguese man-of- 

 war is sometimes driven up from the tropic seas and 

 stranded. It is one of the most interesting of the Med usee 

 family ; armed with poison-filled tentacles which are its 

 weapons of defense, and by them its food is obtained. The 

 study of the Medusce, either in books or actual life, watch- 

 ing development, will fill many days with delightful em- 

 ployment. In fresh water, common Hydra may be found 

 under leaves of aquatic plants. Cut them in pieces and see 

 their power of reproduction from the severed pieces. Turn 

 them inside out and see the result. 



Chapter VIII. — Origin of pearls was formerly ac- 

 counted for by drops of dew becoming solidified. Pearls 

 are formed over hard, ofl'ensive matter within the folds of 

 the mantle, also secreted and used as nacre by the animal 

 in mending points of irritation. Pearls most highly 

 esteemed by all nations and at all times. Pearls are of 

 various colors and each color has its peculiar votaries. 

 The pearl Cleopatra drank questioned by science. 



The rainbow shells of the Haliotidce called Awabi in 

 Japan, abalone in California. The iridescence of their 

 nacreous lining due to the laminations of nacre secreted 

 by the animal and irregularly overlapping in delicate 

 films. Read Precious Stones, by Harry Emanuel. 



Chapter IX.— Term Algce now includes much less 

 than formerly, many specimens once held as vegetable 



