Abstract
The development of the nervous system can be studied only if the age of the embryo is exactly known. Since it is difficult to control reproduction in female cats, we tried to time fertilization very precisely to within one hour by using either artificial insemination, or by mating females in oestrus induced by light programming. In one trial, this programming was associated with male or female stimuli according to the work of McClintock (1971, 1978, 1984) and Preti et al. (1986).