スナヤツメの人工受精と初期発生

Artificial insemination of the planeri lamprey was tried every Spring in the years from 1950 to 1953. In 6 cases of 17 cases many hatched larvae were obtained. On the change of the appearance the early development of the fertilized eggs was observed in each time with the microphotography. In the following the time of the beginning of each developmental stage was shown. The Ist cleavage: 5～5 1/2 hours after insemination The 2nd cleavage: 6 1/2 hours after insemination Tte 8-cell stage; 8 hours after insemination The 16-cell stage; 10 hours after insemination The 32-cell stage: 11 1/2 hours after insemination The 64-cell stage: 13 hours after insemination The Morula-stage: 20 hours after insemination The Blastula-stage: 36 hours after insemination The Gastrula-stage: 58 hours after insemination The Neurula-stage: 4 days after insemination Appearance of the head, Strengthening of the Neck: 6～7 days after insemination Hatching: 8～9 days after insemination Wandering: 2weeks after insemination