S. I. iStnith — Early Stages of the American Lobster. 381 



Figure 3. — One of the legs of the second pair, tliird stage, enlarged 20 diameters. 



Figure 4. — Base of one of the legs of the second pair, earliest condition of the adult, 

 enlarged 20 diameters; a, 6, c, refer to the same parts as infigure 2. 4a, 

 terminal portion of the same leg, enlarged the same amount. 



Figure 5. — One of the posterior cephalothoracic legs, second stage, enlarged 20 diam- 

 eters ; a, exopodus ; c, branchial appendage ; 5a, terminal portion of the 

 same leg, enlarged 40 diameters. 



Figure 6. — Terminal portion of same leg, first stage, enlarged 40 diameters. 



Figure 7. — Same, third stage, enlarged 40 diameters. 



Figure 8. — Same, earliest condition of the adult, enlarged 20 diameters. 



Figure 9. — Terminal portion of the anterior cephalothoracic leg of the right side, first 

 stage, enlarged 40 diameters. 



Figure 10. — Same, second stage, enlarged 20 diameters. 



Figure 11. — Same, third stage, enlarged 20 diameters. 



Figure 12. — Same, earliest condition of the adult form, enlarged 10 diameters. 



Plate XYIII. 



Figure 1. — Extremity of the abdomen seen from above, first stage, enlarged 20 diam- 

 eters, la, portion of one of the angles enlarged 40 diameters, showing 

 the plumose marginal sets. 



Figure 2. — Same, second stage, enlarged 20 diameters. 



Figure 3. — Right side of the same, third stage, showing the appendages of the penulti- 

 mate segment, enlarged 20 diameters; 3a, marginal setse of one of the 

 appendages of the penultimate segment, enlarged 50 diameters. 



Figure 4. — Terminal segment of the abdomen and appendages of the penultimate seg- 

 ment on one side, earliest condition of the adult form, enlarged 20 diam- 

 eters. 



Figure 5. — One of the appendages of the third segment of the abdomen, second stage, 

 enlarged 30 diameters. 



Figure 6. — Same, third stage, enlarged the same amount. 6a, one of the rudimentary 

 marginal seta;, enlarged 100 diameters. 



Figure 7. — Same, earliest condition of the adult form, enlarged 20 diameters. 7a, one 

 of the marginal setse enlarged 100 diameters. 



Figure 8. — Lateral view of the fourth segment of the abdomen, showing the dorsal 

 and lateral spines, first stage, enlarged 20 diameters. 



Figure 9. — Diagram of a section of the same segment seen from behind, enlarged 30 

 diameters. 



Figure 10. — Lateral view of the middle portion of tlie abdomen, earliest condition of 

 the adult form, enlarged 8 diameters. 



