472 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
EXPLANATION OF PLATES. 
All the tigure9 except those of plate xcn and 108a and 1086 were drawn by the author with the aid of the Abbe camera, 
either from living specimens or from balsam preparations. 
al. Alimentary tract. 
an. Anus. 
ao. Dorsal aorta. 
au. Auditory capsule. 
aur. Auricle. 
au. v. Auditory vesicle. 
br. 1, 1 First, second, etc., 
br. 2, etc. 5 gill-slit. 
ca. v. Cardinal vein. 
cer. Cerebrum. 
c6. Cerebellum. 
ch. Notochord. 
ep. Epiblast. 
fb. Fore brain. 
hb. Hind brain. 
ht. Heart. 
hy. Hypoblast. 
hyp. Hypophysis. 
K. r. Kupfi'er s vesicle. 
1. Liver. 
mes. Mesoblast. 
n. Spinal chord. 
nc. Neural canal. 
ne. c. Neurenteric canal. 
nl.per. Periblast nuclei. 
ol. Olfactory organs. 
■ op. Optic vesicle or stalk. 
per. Periblast. 
pi. Pectoral. 
vo. Sex cells. 
pro. Protovertebra. 
s. c. Segmentation cavity. 
8. d. Segmental duct. 
so. Somatic mesoblast. 
sp. Splanchnic mesoblast. 
spi. Spiracular slit. 
spn. Spermatozoa. 
thy. Thyroid. 
v. ao. Ventral aorta. 
ven. Ventricle. 
yk. Yolk. 
yk.pr. Yolk protoplasm=yol k 
nucleus. 
yk. v. Yolk vesicle. 
Plate XCII. 
Fig. 1. Damalichthy8 argyrosomus Girard, $ • Friendly Cove, British Columbia. 
Fig. 2. Bhacochilm toxotes Agassiz, 9 • Monterey, California. 
Fig. 3. Cymatogaster aggregates Gibbons, 9 . Fort Wrangel, Alaska. 
Fig. 4. Anal fin of the male of a Hyper prosopon. 
Plate XCIII. 
Diagram showing the process of maturation, conjugation, and segmentation in Protozoa and Metazoa 
and the segregation of the macronuclear substance. See p. 446. 
Plate XCIV. 
Fig. 1. Surface view of a living egg at the completion of the first segmentation. 
Fig. 2. A living egg at the end of the second segmentation, seen from the entodermic pole. The four 
blastomeres are seen to project beyond the yolk, which is represented as a transparent object. 
The yolk nucleus yk. pr. shows projections which extend in between the yolk particles. 
Fig. 3. Another egg from the same ovary, showing resting nuclei. 
Fig. 4. Cross-section (somewhat oblique to the dividing plane) of a two-celled egg showing amphiaster 
of second division. 
Fig. 5. Another section from the same egg showing the complete division of. the germ from the yolk 
and the total segmentation of the germ. Only the germinal portion shaded. 
Fig. 6. Living egg with 8 cells. Supposed sequence of cleavage planes indicated by Nos. 1, 2, 3. 
Fig. 7. A diagrammatic cross-section of a similar egg from a section of a wax model constructed from 
oblique sections. 
Fig. 8. A diagrammatic representation of the surface lines of the cleavage planes at the end of the 
third cleavage, viewed from the ectodermic pole, constructed from fig. 6 and from the wax 
model mentioned under 7. 
Fig. 8a. Diagram of ordinary teleost germ at end of third segmentation. 
Fig. 9. Section of an 8-cell egg. The probable plane of the section is indicated in fig. 6, x-y. The egg 
was cut into thirteen sections, of which this is the fifth, x 4. 
Fig. 10. Another sectiou, the tenth, from the same egg, indicated by x'y'. 
Figs. 11-14. A series of optic sections of an egg with 16 cells; the planes of the sections pass through 
the resting nuclei. (Figs. 13 and 14 are on the next plate.) 
Plate XCV. 
Figs. 13, 14. Optical sections of an egg with 16 cells. 
Fig. 15. Surface view of early stage of segmentation from a living egg. 
Fig. 16. Slightly later stage, surface view from a living egg. 
Fig. 17. Surface view of another egg. 
Fig. 18. Section of an egg with about 32 cells. 
Fig. 19. Median vertical section of an egg with 32 to 64 cells. 
Fig. 20. Two sections toward the margin from fig. 19. 
Fig. 21. Section slightly oblique from the horizontal from an egg with 32 to 64 cells. 
Fig. 22. Section slightly oblique to horizontal of an egg with about 50 nuclei. Upper portion of sec- 
tion touches yolk. The probable first and second cleavage planes indicated by heavy lines. 
