412 THE AMERICAN MONTHLY [Dec. 



fin is an important character for distinguishing different 

 species of fisli. Make a study of the distribution of 

 color, and note that all the parts which would be visible 

 from below are silvery white, while all those that would 

 be seen from above are black; notice accurately the 

 boundaries of these two colors. Do you think of any ad- 

 vant{i<:^e from this distribution of the color? Is it true 

 generally of animals? Cf "Protective Coloration." Draw 

 a side view of the smelt and show and index as many of 

 these points as possible. Compare the smelt with other 

 vertebrate animals (such as shark, skate, gar-pike, stur- 

 geon, pike, bass, salamander, fi'Og, lizard, snake, turtle, 

 ostrich, eagle, duck, crane, sparrow, porpoise, seal, dog, 

 horse, cow, bat, squirrel, ele[)hant, mouse, ape and man. 

 Can you make close comparisons in structure between the 

 smelt and invertebrate animals such as clam, snail, angle- 

 worm, cray-fish, butterfly? 



2. The Head. — In all the vertebrates (Craniota) 

 the head presents two parts, the craniu7n, which lodges 

 the brain; and the face, which includes the nose and eyes 

 above and the mouth and throat below.- In the smelt 

 these parts are all present in the head, but the cranium 

 is covered up by the face and lies in the upper and 

 hinder portion of the head; the face will be taken up for 

 study first. 



3. The Nose, — as usual presents two chambers, ojien 

 to the exterior by two small nostrils anterior fiareft easily 

 seen. Cutaway the skin around one of these nostrils 

 and you will uncover a small olfactory pit lined with 

 white colored olfactory mucous membrane. Search in the 

 olfactory pit, also in the mouth chamber to deter njine 

 whether there is a passage from the nostrils to the throat 

 posterior nares as in the other vertebrates. 



4. The Eyes. — Examine one of the eyes in its orbit 

 or socket in the side of the head. Are there any lids? 



