130 ORIGIN OF SOMATIC 



perches in special cages, but pull the tail feathers 

 gently every morning in order to cause them to grow 

 longer. One question which I had to investigate on 

 my specimens, hatched from eggs obtained from 

 Mr. Sparks, was the relation of the growth of the 

 feathers to the moult which occurs in ordinary birds. 

 My experiment consisted in keeping two cocks, A 

 and B, the first of which was left to itseK, while in 

 the second the feathers were gently pulled by stroking 

 between the finger and thumb from the base out- 

 wards. The feathers in the tail were seven pairs of 

 rectrices, two rows of tail coverts, anterior and 

 posterior, four or five pairs in each row, a number 

 of transition feathers : all these were steel-blue, 

 almost black ; in front of them on the saddle were a 

 number of reddish yellow, very slender saddle hackles. 



In September 1901, when the birds were just over 

 three months old, the adult feathers of the tail were 

 all growing. The growing condition can be distin- 

 guished by the presence of a horny tubular sheath 

 extending up the base of the feather for about one 

 inch. When growth ceases this sheath is shed. In 

 cock A growth continued till the end of the following 

 March, when the longest feathers, the central rectrices, 

 were 2 feet 4J^ inches long. One of the feathers — 

 namely, one of the anterior tail coverts — was acci- 

 dentally pulled out on 11th February 1902, when it 

 was 15 J inches long and had nearly ceased to grow 

 and formed its quill, and it immediately began to 

 grow again and continued to grow till the following 

 September, when it was accidentally broken off at 

 the base : it was then 18 inches (44*5 cm.) long. 



The effect of stroking in cock B was to pull out 

 from time to time one of the growing feathers. Of 



