172 6:1:10:2 A preliminary arrangement of data in re- gard to period of gestation of Humpback On May 22 a foetus 2 inches long from a Humpback – on the 1st June a foetus 8 inches long was taken – on June 13 a foetus about 18 inches long was taken – on June 27 a foetus 45 inches long taken – The calf must be from 10 to 12 feet long when born, according to the size of Cuvierius – not supposing that in whale which contained the foetus 2 inches long, used about the first of April; from April to July is 3 months The growth from April to July is 2 45 inches which makes 15 inches per month – supposing the calves to be 14 ½ feet long when born then the mothers would be dry young for about 9 ½ mo. This rate of growth is probably a little too rapid, making the period of gestation about 12 or 14 months. On June 16 a calf 25 feet long which was still sucking was killed while the mother. This calf must therefore have been born at least year previous