176 TRANSACTIONS OF THE [may 11, 
Fia. 3. The same stage, showing variation in relation of asters to nucleus. 
Fic. 4. Much later stage. The. tetrad groups have now been established, 
leaving a mass of discarded chromatin. The sperm head is shown at ¢. 
Fia. 5. First polar spindle during halving of tetrads. Sperm head at ¢. 
Fia. 6. First polar telophase. Sperm head and aster ( g). 
PLATE X. 
Fic. 7. Second polar spindle, still tangential in position. Slightly later 
than Fig. 6 
Fic. 8. Second polar spindle. Spermhead with amphiaster (¢). 
Fic. 9. Second polar telophase, showing centrosomes divided. Sperm- 
head and amphiaster ( ¢ ). 
Fic. 10. Shortly before copulation of pronuclei, showing male pronucleus 
( g) with powerful asters, and the female vesicles ( 2 ) deve oid of asters. 
Fic. 11. Copulation of pronunclei. 
Fic. 12. Somewhat later stage, segmentation nucleus elongating. 
PLATE XE: 
Fic. 13. Fully formed first cleavage figure, showing centrosomes already 
divided and surrounded by the darker area, nearing the periphery of the 
centrosphere. 
Fic. 14. Commencement of anaphase. Centrosomes or periphery of cen- 
trosphere. 
Fic. 15. Stage just previous to mid anaphase, minute amphiaster forming 
about the centrosomes. 
Fic. 16. Mid anaphase, amphiaster elongated. 
Fia. 17. Vesicles previous to fusion. 
Fic. 18. Vesicles fusing. 
ANATOMY OF THE EAR OF THE DOG-FISH (GALEUS 
CANIS.) PRELIMINARY PAPER. 
By WarRREN H. EVERETT. 
This work was begun at the Marine Biological Laboratory, 
Wood’s Holl, Mass., “during the summer of 1893, at the sugges- 
tion of Prof. Howard Ayres, of the University of Missouri. It 
was continued at Hamilton College under the supervision of 
Prof. A. D. Morrill, and brought to its present state of com- 
pleteness at the Biological Laboratory of the New York Uni- 
versity. 
The auditory capsule of the dog-fish (Galeus canis) is situated 
on either side of the head just outside of the brain cavity, the . 
anterior wall of the capsule forming the posterior wall of the 
orbit. A line drawn from the posterior corner of the eyelids 
would touch the most anterior part of the ear. 
The capsule consists of a mass of hyaline cartilage, lined in- 
