Quantitative observations on pig embryos of known ages

The lengths and weights of 241 pig embryos, aged 26–109 days, were recorded; the pregnant sows were from a mixed herd of Landrace, Large White and Wessex stock and some of their crosses. 2. An empirical linear regression of length on age was estimated (equation 1); the relation between weight and age was represented by a polynomial weight and age was represented by a polynomial (equation 2). We thank Mr A. S. Cray and the other directors of Unigate Ltd. for giving us the pigs; Mr P. Sedgewick of that Company gave us excellent co-operation. Prof. C. W. Ottaway and Dr P. Radford helped us throughout the investigation.