. Carnegie Institution of Washington publication. 48 CHIM/EROID FISHES AND THEIR DEVELOPMENT. FERTILIZATION. Fertilization begins, as in sharks, in the uppermost portion of the oviduct and continues throughout the period of the formation of the capsule.* The earliest stage in the writer's material was obtained from a capsule like that shown in plate iii, fig.^'i 3, earlier stages not having been handled successfully. Late stages were secured 44 45 "fi^ ^^'^ ^^^'WtW 1 Jv &^'%'i(S^ ,^ â 'i 45^ 45B 46 46A -r "^i^ife*^ 47 47J. .«) '^ f'Sv- ,<-, ^^j^^"^ © '^"^^'"^^
. Carnegie Institution of Washington publication. 48 CHIM/EROID FISHES AND THEIR DEVELOPMENT. FERTILIZATION. Fertilization begins, as in sharks, in the uppermost portion of the oviduct and continues throughout the period of the formation of the capsule.* The earliest stage in the writer's material was obtained from a capsule like that shown in plate iii, fig.^'i 3, earlier stages not having been handled successfully. Late stages were secured 44 45 "fi^ ^^'^ ^^^'WtW 1 Jv &^'%'i(S^ ,^ â 'i 45^ 45B 46 46A -r "^i^ife*^ 47 47J. .«) '^ f'Sv- ,<-, ^^j^^"^ © '^"^^'"^^^^a^ Fig. 44.âDetail of late fertilization stage, showing male nucleus in the process of approaching the egg nucleus. A club-shaped centrosome surrounded by astral rays appears at (right) side of nuclear membrane. X 475. Fig. 43.âDetail of section similar to the last. A well-marked vacuole (artifact ?) appears at one end o( nucleus. Fig. 43A.âSperm nucleus with aster from section similar to the preceding. Fig 45B. -Sperm nucleus from stage similar to foregoing. The center of aster is to be found in the section below present one. Fig. of sechon shown in lig. 34. Sperm nucleus has divided amitoticaily. This at first suggests a stage of copulating pronuclei. Fig. 46A.âEgg and sperm nuclei in apposition. Rays not conspicuous. Fig. 47.âEarly prophase of segmentation nucleus. Two asters are present, one of which (the right) contains two centrosomes. Fig. 47A.âEarly segmentation stage. Section passing through segmentation nuclei. No surface furrows are as yet present. X 190- from capsules about as shown in plate iii, fig. i6. In the present account the stages may conveniently be referred to as early, middle, and late. An early stage is shown in surface view in plate iv, fig. i8, magnified about 15 diameters. This was drawn from a living egg and shows the germinal area somewhat misshapen, due to rupture of the vitelline membrane, f The germinal area is not sharply
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