Observations were made on four Suffolk lambs from birth to 14 months of age, wool and skin samples being taken periodically. The lambs were on a high nutritional plane and grew well throughout the experiment.

1. There is good agreement between estimates of growth based on body weight, calculated surface area, and expansion of tattooed squares.

2. Fibre Type Arrays were Valley or Plain.

3. Benzene tests showed considerable medullation in the fleeces of all the lambs, mainly in the posterior parts. There were practically none on the shoulder.

4. The weight of keratin produced daily per unit area of skin reached or exceeded the figure given as maximal by Galpin (1948) in only six samples, of which four were grown prior to 1 month old.

5. The follicle population completes its development early, only a few secondary follicles being added after birth. The definitive S/P ratio is 5/, which is similar to the Leicester, and lower than in the Romney breed. The follicle density, although high at birth, is lower than in the Romney or Leicester, after 9 months old. Both S/P ratio and follicle density are higher than in the Blackface breed.

6. The transitory black colour of the birth-coat of Suffolk lambs is due to pigmentation of the tips of many fibres; this may affect any type of fibre from haloes and sickles to histerotrichs. With very few exceptions all follicles cease to produce pigmented fibre at or shortly after birth of the lamb. Large amoebic melanoblasts are present in the skin.