Abstract
Nineteen bitches were killed at varying time intervals after mating for the recovery of ova in order to examine their development, cleavage and transport in the oviducts and uterus.
All bitches were mated 36 hr after the onset of estrus; therefore interaction between ova and sperm is expected to occur just after ovulation.
Ova were recovered between 24 to 216 hr after ovulation presumed by laparotomy, by flushing the oviducts or uterus using physiological saline solution and examined microscopically.
The results obtained are as follows.
1. The bitch egg just after ovulation was at the stage of a primary oocyte and first polar body was extruded 4872 hr after ovulation. The ovulated egg retained its covering layers of follicle cells untill 24 to 48 hr, then follicle cells decreased in number up to 120 hr, no follicle cells were found at 168 hr.
2. Fertilized ova were transported into the middle part of the oviduct 24 to 48 hr after ovula-tion. Cleavrge began from 72 hr in the middle or distal part of the oviduct, and ova were in the 2-cell stage at 96 hr, in the 36-cell stage at 120 hr, 8-cell stage at 144 hr, in the 8-16-cell stage at 168 hr and 16-cell stage at 192 hr in the distal part of the oviduct. Thereafter they were trans-ported into the uterus in the morula stage at 204 to 216 hr.
3. In 3 out of 19 bitches (15%), degerative ova were found in the distal part of the oviduct, probably due to the previous ovulation. These results suggest that the ova in the bitch may be retained in the oviduct for more than 6 month after ovulation.
