The development of the follicle population in lambs of the English Leicester and Romney breeds has been studied in relation to the developing fleece, skin and fibre samples being taken at four ages, namely at 1, 3, 6 and 9 months after birth. The technique used in obtaining skin samples and preparing them for examination, and of obtaining estimates of the follicle population, and the data thus obtained, are presented and discussed in the foregoing pages. Although as a result of technical difficulties and other misfortunes the complete set (1943). The follicle group in the samples taken at 1 month old showed primary follicles on the ental side, large secondary follicles along the ectal margin, and smaller secondaries, or secondary follicle primordia, situated towards the centre of the group. Accessory structures (sweat gland, arrector muscles) usually associated with primary follicles only, may occasionally be found in connexion with follicles situated on the ectal side of the follicle bundle, and apparently corresponding to large secondary follicles. Attention is drawn to the fact that a group of secondary follicles normally develops around the ectal aspect of each primary follicle, whether the latter is solitary or one of a couplet or trio. It is suggested that the ‘primary group’ (one primary and its associated secondaries) is a fundamental unit of the fleece, although generally included within the trio group.