The pronephros of Scyllium canicuia. 259 
is swollen, and its somatic wall is slightly grooved. This groove is the 
early condition of the pronephros in the region opposite the middle of 
the protovertebrae. 
Fig. 3 (Section 1,153). The Segmentalbläschen are well shown in 
this figure. 
Fig. 4 (Section 1,154). On the right side the section passes through 
the posterior region of protovertebra VII on the animal’s left side. The 
out-pushing of the somatic mesoderm is quite obvious. On the left side 
the section passes through the anterior region of protovertebra VII 
(right side). The pronephric region is present, though not very pro- 
nounced. 
Fig. 5 (Section 1,155). On the right side of the figure the extreme 
posterior end of protovertebra VII is cut through. The pronephrie rudi- 
ment is quite distinct. 
Fig. 6 (Section 1,156). On the right side in this figure the rudiment 
is seen in the region between protovertebrae VII and VIII (left side): 
its presence in this region proves that the pronephric outgrowth is not 
segmental in origin. 
Fig. 7 (Section 1,157). This section passes through the pronephric 
rudiment in the region of the anterior end of protovertebra VIII (right 
side of figure), and through the region opposite the posterior end of 
proto. VII (left side of figure). 
Fig. 8 (Section 1,158). The pronephric outgrowth is very prominent 
on the right side of this figure. 
Fig. 9 (Seetion 1,159). On the left side the rudiment is shown in 
an intersegmental region (between proto. VII and VIII). On the right 
side the section shows the middle of proto. VIII on the embryo’s 
left side. 
Fig. 10 (Section 1,160). The groove-like nature of the rudiment 
is much more apparent on the right side (opposite middle of proto. VIII) 
than it is on the left side (opposite front end of proto. VIII right side). 
Fig. 11 (Section 1,161). The pronephros is well-marked in this 
section. 
Fig. 12 (Section 2,1). The section next after 1,161. The posterior 
region of proto. VIII (left side) is seen on the right of this figure, and 
the middle region of proto. VIII (right side) is seen on the left of the 
figure. 
Plate 19% 
Fig. 13 (Section 2,2). Shows the pronephros in an intersegmental 
region on the right side. 
Fig. 14 (Section 2,3). On the left of this figure the pronephros 
near the end of segment VIII on the embryo’s right side is visible. 
Zool. Jahrb. XXXVII. Abt. f. Anat. 17 
