THE CRAYFISH. 31 



and is so developed as to cover the other cephalotho- 

 racic segments. 

 16. Make, side by side, three drawings of the crayfish, — 

 a dorsal, a ventral, and a lateral view, — naming all 

 parts. 



CRAYFISH CARD. 



Take an entire crayfish ; separate all its parts, and paste 

 them on a card, as in the case of the grasshopper ; arrange 

 the eyes, antennae, antennules, mandibles, maxillae, maxilli- 

 peds, and thoracic legs, symmetrically about the carapace. 

 Make a paper bridge on which to rest the carapace. 

 Separate the rings of the abdomen, string them on the 

 paper bridge, and place opposite each its appendages, 

 remembering that the side parts of the tail-fin are appen- 

 dages of the sixth ring. Draw in your note-book all the 

 parts as arranged on the card, with the name beside each 

 part. 



INTERNAL STRUCTURE OF THE CRAYFISH. 



The better dissecting pans have a thick layer of wax in 

 the bottom, or a sheet of cork weighted with lead, to 

 which specimens may be pinned, and dissected under 

 water. Very good cheap dissecting pans may be made 

 as follows : take oyster-cans that have been opened on one 

 side, and cut out this side, leaving a margin half an inch 

 wide. Bend this margin down inside. Cut a piece of 

 shingle or cigar-box cover for a false bottom, leaving it a 

 little long, so it will wedge in tightly and not float up 

 when water is poured in. 



For this work use lobsters, or as large crayfishes as possi- 

 ble. Place the crayfish in the dissecting pan, and cover it 



