INVERTEBRATA. 409 



called, the wood-louse, is found every place, in cellars and 

 gardens, under stones, logs, etc. Its food is decomposing 

 vegetable matter. " The female carries her eggs in an oval 

 sack beneath, where they are hatched " 



PORCELLIO spinicornis. This is also called the sow-bug. 

 It has the same habits as the Oniscus. 



SECOND DIVISION. ENTOMOSTRACA, called by the older 

 naturalists, insects with shells. This group of animals is 

 aquatic, inhabiting fresh water, and is generally micro- 

 scopic. They have peculiar organizations, and sometimes 

 possess a hundred feet. 



ORDER I. BRANCHIOPODA, (Gill-footed.) 

 Mostly microscopical. The old genus Monoculus, Linn., 

 belongs here. 



ORDER II. PCECILOPODA, (Yarious-footed.) 



Their habitat is said to be on aquatic animals, and gene- 

 rally on fishes. This order is divided into two families 

 First, Xiphosura, in which is the genus Limulus ; and 

 second, Siphonostoma. There are two genera of this order, 

 and they are parasitical ; one, the Caligus, is called the Fish- 

 louse. 



This is the old Cuvierian arrangement of the crustaceans. 

 The area of knowledge in this department has been im- 

 mensely enlarged since this classification was made. 



More recent classifications of the crustaceans place a new 

 group between Brachyura and Macrura of the first order 

 Decapoda, called Anomura ; also, next to Po3cilopoda, an 

 order Fhyllopoda, Lophyropa, Branchiopoda, (old,) which 

 contains Branchipus stagnalis, " common in most stagnant 

 pools of fresh water," and lastly, order Ostrapoda, many of 

 which are also found in fresh water pools. 



New and vigorous laborers are now in the field with the 

 enthusiasm of youth,* with culture and genius, and the hope 

 of the science of the hour is, that this wonderful world of 



* The accomplished and ingenuous youth, Wm. Stimpson, is doing 

 good work in this department. Long arid successfully may he labor. 



35 



