1. Observations, mainly concerning the fleece and pigmentation, were made on about 80 F1 Merino × Herdwick sheep. Of these, nine were used for intensive fleece studies, and skin samples were obtained from six.

2. Pigmentation in all the F1 lambs was greatly reduced as compared with the Herdwick breed, the majority being entirely white on the main fleece area, with varying amounts of black and brown speckling on the face, legs and neck. A few were entirely white, like the Merino. The shade of colour of the Herdwick dam did not affect the amount of pigment on her half-Merino offspring.

3. The fibre type array most frequently encountered was one not previously described, which has been named Incline. Fine Plateau arrays were also frequent, especially on the mid-side and britch positions. Other arrays which occurred were Coarse Plain, Fine Plain, Ravine, and Coarse Plateau.

4. The hogg fleece weights averaged approximately 4·5 lb. for females and 5 lb. for males, which is about double the average weight of Herdwick hogg fleeces. In general appearance they showed some superficial resemblance to Romney and Corriedale fleeces, but there was much variation between individuals. None closely resembled either parental fleece type, but the Merino influence was much more manifest than the Herdwick. Kemp, if present, was usually long and fine, resembling hair.

5. Growth of the experimental animals was normal. In an endeavour to assess conformation, measurements were taken on a few sheep, and compared with similar measurements on Herdwick and Swaledale.

6. The follicle population showed characteristics of both parental breeds, and varied greatly between individuals. The highest S/P ratio was 9·0, with a follicle density of 3000 per sq.cm. In comparison with the British breeds previously studied, autumn and winter fibre shedding was delayed and reduced in the crossbreds.

7. Thetotal number offibresper tattooed square remained stable after sample 2 (about 2 months old). There was no significant difference between sheep or between samples in percentage of coarse, medium and fine fibres, but there was a highly significant difference between positions S (shoulder), A (last rib), B (britch) and D (rump). Mean fibre density was approximately 3000 per sq.cm., and mean fibre quality proportions (by number) in the A position was coarse 10%, medium 24% and fine 66%.

8. Nearly 85% of the total clean weight of wool produced was grown in the late spring and summer months. The total wool grown was divided into three qualities and the proportion of the total weight derived from each quality was coarse 23·69%, medium 41·21%, and fine 35·10%. The distinction between the three qualities was often quite doubtful and never as clear as in the Herdwick breed. There were significant differences in proportions of coarse, medium and fine wool, between regions, between seasons and between sheep.

9. In the discussion, which concludes the series of studies of fleece and follicle population, the following topics are treated: error of estimate of proportions in work of this kind; time of development of post-natal secondary follicle, and theories of the possible influence of primary follicles on the development of secondary follicles; post-natal growth in size of follicles in Merino and other breeds; autumn moult; recapitulation in follicles during regrowth after fibre shedding; significance of fibre type arrays; origin of the Longwool breeds; protective birth-coats; pigmentation; ‘lift’ in British wools; and the possibilities of establishing a breed with the Merino type of fleece on British hill and mountain farming areas.