172 MORPHOLOGY OF INVERTEBRATE TYPES 



in some specimens in the mid-dorsal line under the integument 

 in the abdomen. 



2. Turn the specimen on its back and make a half page 

 drawing showing the ventral surface. Label chelicera with 

 fangs, pedipalpi with maxillary lobes, lower lip, sternum, legs, 

 pedicel, lung-books, genital fold with genital opening in middle 

 and a stigma at each end, epigynum, anterior or lower spin- 

 nerets, posterior or upper spinnerets, and anal tubercle. The 

 tracheal spiracle is difficult of detection, but may be recognized 

 by the direction of the hair surrounding it. The median spin- 

 nerets are not visible. Label the somites with the aid of the 

 description given on a previous page. Label all joints of a 

 pedipalp and of a leg. 



3. Take the spider with your left hand and examine it through 

 a magnifying lens from in front. Make a drawing showing out- 

 line of carapace and chelicera. Label clypeus, anterior and pos- 

 terior rows of eyes; represent the shape of each row by a dotted 

 line passing through the centres of the eyes. This drawing 

 will represent the relation of characters as used by systematists. 



4. Repeat the same drawing omitting the dotted lines. Make 

 a single dotted line between the eyes, dividing them into two 

 groups corresponding with the somites. The second somite has 

 only one pair of eyes. Label somites. 



5. Remove two terminal joints of a leg, boil them in 20% 

 potassium hydrate, wash in water, place on a slide in a drop of 

 glycerine and examine under cover glass through the microscope 

 (200 diameters). Make a drawing showing claws. 



6. Examine the joints under high power (400 diameters), find 

 a common hair, a plumose hair, a spine and a trichobothrium. 

 Make drawings of them and label. 



7. Boil the rest of the leg in 20% potassium hydrate and find 

 the lyriform organs. Make a drawing showing them. 



8. Remove the spinnerets together with adjoining tissue and 

 treat in the same manner. Examine under low power and make 

 a drawing showing all six spinnerets. 



