58 Laboratory Guide in Zoology 



of each of the antennules find a peculiar structure, 

 the organ of equilibration. 



IX. — Comparison of Appendages. Remove one of the 

 chelae, study and number its parts. Remove, study 

 in the same way, and compare with the chelse, one of 

 the first or second walking legs. Go through the same 

 process with one of the fourth walking legs. Review 

 the entire row of appendages, and note that all are in 

 pairs, and that they are nearly all jointed, and possess 

 branched terminations. Regarding each pair of ap- 

 pendages as representing a single somite, determine the 

 number of somites of which the lobster may be said to 

 be made up. Draw a side view of the animal. 



INTERNAL ANATOMY 



X. — Muscular System. Remove, with strong knife or scis- 



sors, the tergites of the abdominal segments, cutting 

 away the muscles attached to them. The white masses 

 filling the abdomen are the strong muscles, and form 

 the edible flesh of the lobster. 



XI. — Blood System. Remove in a similar manner the 

 entire top of the carapace, being very careful to dis- 

 turb n'bne of the organs below. Near the centre of 

 the thorax, find exposed a soft, plastic, somewhat angu- 

 lar body, the heart. Find the colorless, hence some- 

 what indistinct, arteries, running forward, laterally, and 

 backward from the heart. Follow the artery running 

 backward, by pushing aside the muscles between which 

 it lies, and observe its branches supplying the surround- 

 ing tissues. The straight tube below, and attached to 

 the blood-vessel, is the intestine. 



XII. — Reproductive System. Carefully remove the heart, 

 and find directly below it either the testes or the ova- 



