lo PHYLUM ARTHROPODA 



Exercise 8. With strong forceps remove the dark-colored mandibles 

 and draw the inner surface of one of them on a scale of 5. 



Exercise 9. Remove the maxillae, which lie just back of the mandi- 

 bles, being careful to take out the entire structure. Mount them 

 on a glass slide in water with the posterior side uppermost, and 

 examine them under the microscope. Note the following parts : 

 the basal segment, or cardo, by which the maxilla articulates with 

 the head ; the stipes, the broadest segment of the structure ; the 

 inner and the outer lobes, which project from the distal edge of 

 the stipes ; and the mgixillary palp, which projects from the lateral 

 edge of the stipes. Draw a maxilla on a scale of 5 and label all of 

 these parts. 



Exercise 10, Note between the maxillae and just in front of the labium 

 a small median projection, the hypopharynx. Remove the labium, 

 taking care to leave none of it in the animal, and mount it on a slide. 

 Note the basal segment, by means of which the labium articulates 

 with the head, and the two jointed labial palps, which project from 

 the lateral edges. The labium is a second pair of maxillae fused in 

 the median line. Trace the homologies between the parts of the 

 labium and those of the maxillae. Draw the labium on a scale of 

 5 and label its parts. 



Internal Anatomy. Take the grasshopper in the hand and with 

 a pair of fine, sharp scissors cut a slit through the body wall a 

 little to one side of the mid-dorsal line from one end of the body 

 to the other, using great care not to injure the organs within. 

 Place the animal, dorsal side up, in a shallow pan with a wax- 

 covered bottom containing water. First, with two strong pins, 

 pin the head to the wax and then the extreme hinder end of the 

 body ; then carefully spread the cut edges of the body wall as 

 widely as possible to the right and left and pin them down, using 

 many pins on each side. Observe the organs as they lie in the 

 body cavity. In the thorax will be seen the strong locomotory 

 muscles. Lying immediately beneath the dorsal abdominal wall 

 in the median line is the heart ; this may have been destroyed by 

 the incision, but if not, it may be recognized as a narrow, trans- 

 parent tube of the diameter of a needle, flanked by paired tri- 

 angular muscles which hold it to the body wall. Immediately 

 beneath the heart is a loose network of yellowish, fatty tissue, 



