of the Fishery Board for Scotland. 
311 
DESCRIPTION OF PLATES. 
The figures, except figs. 16 and 17, were drawn by means of the camera 
lucida. 
Reference Letters. 
CL. C. 
alimentary cdiidi. 
ms. 
Q ATY1 TfpC! 
oUli.Il UCO. 
cllJ U.S. 
n.c. 
nenrenterio canal 
fill 
Lb It. 
Ceil . • 
no. 
notochord 
b. 
blood. 
0. 
eye. 
br. 
brain. 
ol.o. 
olfactory organ. 
b.o. 
branchial aorta. 
p.b. 
pineal body. 
b.v. 
blood-vessel. 
p.r. 
pigment layer of retina. 
c. 
claspers. 
r. 
retina. 
e. 
epiblast. 
s.t. 
sensory tubes. 
epi. 
epithelium. 
sp. 
spiracle. 
e.g. 
external gill. 
t. 
tail. 
g.c. 
gill clefts. 
u.c. 
umbilical cord. 
ht 
heart. 
u.f. 
unpaired fins. 
hy. 
hypophysis. 
V. 
trigeminus nerve. 
1. 
lens. 
vii. 
facial nerve. 
m. 
site of mouth. 
viii. 
auditory nerve. 
m.c. 
medullary canal. 
ix. 
glossopharyngeal nerve. 
me.c. 
mesoblast cells. 
X. 
vagus nerve. 
me. 
merocytes. 
Fig. 1. Superficial segmentation. 
Fig. 2. Deep segmentation. 
Fig. 3. Shows segmentation cavity in section. 
Fig. 4. Entire blastoderm of preceding stage, aged thirty-one days. 
Fig. 5. First embryonic thickening, forty days. 
Fig. 6. Embryo of fifty-four days (winter). 
Fig. 7. Embryo of ten weeks (winter). 
Fig. 8. Embryo of eleven and a half weeks (winter). 
Fig. 9. Embryo of twelve weeks (winter). 
Fig. 10. Embryo of about twelve weeks (winter). 
Fig. 11. Embryo of nearly fourteen weeks (winter). 
Fig. 12. Embryo of fourteen weeks (winter). 
Fig. 13. Embryo of thirteen and a half weeks (spring), length 5 '8 mm 
Fig. 14. Embryo of eleven weeks (early summer), length 7 '5 mm. 
Fig. 15. Head end of embryo of E. clavata. 
Fig. 16. Dorsal view of embryo of six months, life size. 
Fig. 17. The same as seen from the ventral aspect. 
Fig. 18. End of an external gill-filament of an embryo twenty-three 
old. x 60 diameters. 
All the figures, except fig. 15, refer to R. batis. 
