The evolution theory . e microgamete(the sperm-cell. Fig. 122, 211) places itself close to one pole of the 216 THE EAOLUTIOX THEORY female macroo-ainete (the egg-cell) and then divides twice in succession,so that four small cells arise (Fig. i23, A-C): of these only onepenetrates into the egg-cell {D, (^ K) and unites with it, the other threecome to nought (7), Mi). What a surprising resemblance this bearsto the twofold division of the mother sperm-cell in multicellularanimals, through which the number of chromosomes is reduced tohalf! In the conjugation itself the thread-like chromosomes of t
The evolution theory . e microgamete(the sperm-cell. Fig. 122, 211) places itself close to one pole of the 216 THE EAOLUTIOX THEORY female macroo-ainete (the egg-cell) and then divides twice in succession,so that four small cells arise (Fig. i23, A-C): of these only onepenetrates into the egg-cell {D, (^ K) and unites with it, the other threecome to nought (7), Mi). What a surprising resemblance this bearsto the twofold division of the mother sperm-cell in multicellularanimals, through which the number of chromosomes is reduced tohalf! In the conjugation itself the thread-like chromosomes of thefemale nucleus are plainly recognizable, while those of the maleremain coiled up (Fig. ii8, D). That the nuclear substance can be separated into chromosomes(ids) even in lowly unicellular organisms was probably first demon-strated by R. Hertwigfor Actinosj^hcerium, a Heliozoon or freshwatersun-animalcule, then by Lauterborn in regard to Diatoms, by Bloch-mann for an indigenous Rhizopod, Euglyplia, and by Ishikawa for.
Size: 2269px × 1101px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
