THE METAMERISM OF NEPHELIS. 6/ 



DESCRIPTION OF PLATE VI. 



Fig. 3 is a diagram of Nephelis lateralis showing the boundaries of the somites 

 in Roman numerals, the annuli in Arabic figures, the nephridiopores {tipk.f.), the 

 boundaries of the clitellum (c/.), and the sexual openings (male ^, female 9). 

 The " brain " and the first two body neuromeres are sketched in to show their 

 relative positions. 



Fig. 4 is a dorsal view of A^. lateralis from Wolf Lake near Chicago, 111., 

 showing the relative size of the annuli, and the number of sensillae as seen in a 

 specimen freshly killed in weak chromic acid. The eyes are represented by cres- 

 centic black areas, as seen in a specimen killed in Haller's fluid. They represent 

 the pigmented part only, the large, clear visual cells extending in a cone-shaped 

 cluster from the concave side. The first pair look forward and outward, the 

 second and third pairs backward and outward. Camera drawing : Zeiss, comp. 

 DC I, obj. AA. 



Fig. 5. Ventral view of the same showing the oral sucker as it appears in 

 a freshly killed and well-extended specimen. Annulus 3 is the first complete 

 annulus. 



Fig. 6. Lateral views of the same showing the incomplete separation of annuli 

 I and 2 and the doubling often seen in annuli 4 and 6. 



Fig. 7. Anal region, dorsal view. Annuli 97, 102, 104, and 106 show well- 

 marked sensillae in specimens freshly killed in weak chromic acid, though the 

 number is not constant. Annulus 104 is double, the posterior half bearing the 

 sensillae. The semicircular area on top of the sucker, the "acetabulum," is finely 

 wrinkled, all traces of annulation being lost. 



Fig. 8. Lateral views of an unusual specimen showing the partial fusion of 

 the narrow annulus 5 with the broad annulus 4. Wolf Lake. 



Fig. 9. Dorsal view of a normal body neuromere, showing the elliptical 

 fibrous part in the middle, the two perforations in it near the median line, the 

 slight groove in the median line passing between them. Faivre's nerve is shown 

 as a narrow line between the two connectives. Two pairs of lateral capsules 

 containing nerve cells lie on either side of the fibrous portion, one lying anterior 

 to each of the lateral nerves. Two ventral capsules are shown under the fibrous 

 portion. The dorsal and ventral roots of the anterior lateral nerve are shown 

 together with the " Leydig's cell "■ lying between the two lateral nerves. (Nitric 

 acid maceration ; slightly stained with borax carmine.) Camera : Zeiss, obj. A, 

 oc. 3. 



Fig. 10. Dorsal view of the "brain," the sub-oesophageal ganglia, and first 

 body neuromere, VII. (Nitric acid maceration.) Camera : Zeiss, obj. AA, oc. 2. 



Fig. II. Tracing of same. The capsules are numbered to correspond with 

 the neuromeres to which they belong. The capsule designated " Symph " con- 

 tributes its fibers to the sympathetic system only. It is not metameric. 



Fig. 12. Side view of "brain" of same specimen, \vith same magnification. 



Fig. 13. Tracing of same ; capsules numbered as before. This view shows 

 the relations of the lateral capsules to the roots of their respective nerves in the 

 "brain," and the same relations as they exist in the body neuromere, VII_ 

 The separation of the lateral capsules, 3. 3., of neuromere III is also shown. The 

 position of the junction between the " brain " and the sympathetic is indicated on 



