. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION IN FUNA AND LOACH CROSS 119 mental eggs. The unfertilized eggs remained without advancing further in de- velopment. A similar situation was reported by Yamamoto (1951) to occur in unfertilized eggs of the dog-salmon. 4. Migration of the male and female pronuclei It is a matter of special note that the migration is more striking in the male pronucleus than in the female pronucleus. The penetration of the spermatozoon occurred always around the top of the animal pole where the micropyle exists. At first the sperm
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FERTILIZATION IN FUNA AND LOACH CROSS 119 mental eggs. The unfertilized eggs remained without advancing further in de- velopment. A similar situation was reported by Yamamoto (1951) to occur in unfertilized eggs of the dog-salmon. 4. Migration of the male and female pronuclei It is a matter of special note that the migration is more striking in the male pronucleus than in the female pronucleus. The penetration of the spermatozoon occurred always around the top of the animal pole where the micropyle exists. At first the spermatozoon was found lying in the periphery of the egg. About 15 minutes after insemination, or following the extrusion of the second polocyte, a migration of the sperm nucleus took place towards the deeper part of the egg, to conjugate with the egg nucleus. The second polar spindle was generally formed near the point of sperm pene- tration. After the extrusion of the second polocyte, the chromosomes left in the egg vacuolized into a vesicular body which was transferred into the female pronucleus. The latter moved slightly towards the center of the egg. About 20 or more minutes after insemination, the two pronuclei conjugated in the place where the female pronucleus already lay. After the conjugation the pronuclei persisted in their places throughout the whole period in preparation for the first cleavage. The pattern of the movement of the female pronucleus as observed in the present material is nearly similar to that reported in the carp eggs by Ojima (1943).. FIGURE 18. Two pronuclei during conjugation, 20 minutes after insemination. X 480. S, male pronucleus. E, female pronucleus. FIGURES 19-20. Pronuclei after conjugation, 25 minutes after insemination. X 240. FIGURES 21-22. Two centrosomes, and the first cleavage at prophase. From eggs about 25-30 minutes after insemination. X 240. P, second polocyte. FIGURE 23. Prophase of the first cleavage. From an egg 30 minutes after ins
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
