Embryology and GeneticsDevelopment and genetics. The egg and the spermatozoon. Cleavage of the egg. Gastrulation. Half and whole embryos. The development of Egg fragments. Single embryo from two eggs. Twins and twinning. Multiple chromosome types. Protoplasm and genes. Larval and foetal types. Parthenogenesis. Regeneration. Localization and induction. The determination of sex. Physiological embryology. |
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Page 19
... becomes broken , the fragment without it fails to become attached to the spindle . In con- sequence it will sooner or later become lost . The spindle with the chromosomes now moves toward the pole of the egg , and assumes there a radial ...
... becomes broken , the fragment without it fails to become attached to the spindle . In con- sequence it will sooner or later become lost . The spindle with the chromosomes now moves toward the pole of the egg , and assumes there a radial ...
Page 67
... become broader and the outer ends narrower , Fig . 33c . In other words : the indi- vidual cells become truncated wedges . Now , if over a part of the elastic outer wall of a blastula the cells should change their form so as to become ...
... become broader and the outer ends narrower , Fig . 33c . In other words : the indi- vidual cells become truncated wedges . Now , if over a part of the elastic outer wall of a blastula the cells should change their form so as to become ...
Page 213
... become a male in this situation . It is true that amongst hun- dreds of larvae kept in sea water , a few may become males - but only after some time . The result may be due to the artificial condi- tions that develop in the cultures ...
... become a male in this situation . It is true that amongst hun- dreds of larvae kept in sea water , a few may become males - but only after some time . The result may be due to the artificial condi- tions that develop in the cultures ...
Contents
Development and Genetics | 11 |
The Egg and the Spermatozoön | 18 |
Cleavage of the | 33 |
Copyright | |
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amphioxus animals annelid antipolar antipole appear archenteron ascidian become birds blastoderm blastomeres blastopore blastula changes character chemical chromo cleavage crescent cut surface determined dextral differentiation diploid divide division early ectoderm egg nucleus embryo embryology endoderm enzymes evidence experimental experiments female fertilization fragments frog frog's egg gastrula genes genetic genic balance germ cells gill slits give rise graft groups half halves haploid hybrid individual inner intersexes inturning invagination kind known larvae later stages layer male mammals materials membrane ment mesoderm micromeres neural plate notochord number of chromosomes organs outer ovary pair parthenogenetic pass piece pigment pluteus polar bodies pole posterior present problem produce protoplasm regeneration region right angles rôle sea urchin sea water set free set of chromosomes sexual shown side single species sperm cells spermatozoön spindle tadpole tail takes place testis tetraploid tion Triton tube twins ventral vesicle wall whole embryo yolk