36 



SCIENTIFIC AGRICULTURE. 



Jaiiuarv, 1921. 



yet completely built \\p the following graph fairly 

 accurately repi'esents what has actually occurred. 



GRAPH III. 



DwaJt-vad . 



' im^-x>iia y\j ^ojl-JaMd . 



' ^oA-QtXyr^id. 



f/gjJ L $UAa I ca^n ^ £i (' KUln '&\eedt>. 



It is probably upon the more or less mixed breeds 

 of sheep thus produced that all modern breeds of 

 sheep are based. The Old Testament record of 

 Jacob's method of breeding is suggestive of "how 

 the sheep got its white coat," while Arab and Moor- 

 ish traditions point to the probable evolution of the 

 Merino breed along the shores of the Mediterranean. 



Broadly, the evolution of the really modem breeds 

 of sheep ihas been based upon. — 



(a) Racial tendency to variation. 



(6) The direct and indirect action of the varied 

 environment tending to produce variation. 



Natural and artificial selection working upon these 

 variations jiiave resulted in the evolution of the typi- 

 cal breeds of sheep probably on the lines indicated 

 in the following graph. 



GRAPH IV. 



Thus the sheep in evidence today are : — 



(a) The Lustre breeds w'.iich have probably 

 been derived from tihe Later Mountain Bree^^ls by 

 actual selection and crossing acting throxigh many 

 generations. Suc^ breeds are the We.nsleydale, 

 Lincoln, Leicester, Long Devon, etc., etc. 



(b) The ]\rountain Breeds — of which the most 

 important are the Blackfaeed and Herdwick. The 

 Welsh is a Mountain sheep with much Down blood 



■ in it and judging from tiie crosses produced be- 

 tween it and the Soay, not very far removed from 

 the pure Soay. The Cheviot, another Mountain 

 breed, has also a strong Down foundation but is 

 nearer to tihe true mountain, — or po.ssibly Lustre- 

 breed — than is the Welsh. It is not likely that 

 there is any truth in the suggestions which .have 



Figure 4. 

 Soay Sheep. 



been made that both the Cheviot and Herdwick 

 breeds, localized on tihe north-east and north-west 

 coasts of England respeetivel.y, have developed 

 from cro.s.ses between the native sheep and the 

 Spanish .sheep w.hieh swam ashore from wrecked 

 ships of the Spanish Armada. Curiously enough, 

 however, in tihe north of Scotland the peasants to 

 this day use peculiar colourings in knitting and 

 weaving which certainly suggest a distinctly 

 Spanish influence. 



(c) The Down breeds are now considered true 

 breeds but almost certainly have blood derived 

 from the Merino sheep presented to George III, or 

 possibly from even earlier Merino sheep. Although 

 this i.s often denied, it is wortih noting that when 

 Professor T. B. Wood, of Cambridge University, 

 in his search for a big sheep carrying a 'heavy fleece 

 of fine wool, cro.ssed t.ae Shropshire (a Down type 

 of sheep) with the Merino, the first cross showed 

 distinct segregation — in other words, arguing on 



i?igure S. 

 Fat-tailed Slieep. 



