Thanks for the challenge - it forced me to go back and check my memory.
This from the RUSI Journal of 1914
In the Canadian context, from my copy of Daniel Dancock's "Gallant Canadians", a regimental history of the 10th Bn CEF, page 12, I gleaned the following:
In early 1915, against an authorized strength of 34 officers and 929 ORs the 10th showed 1124 on it rolls, including 44 officers. It was overstrength prior to going across to France and being blooded at St Julien's Woods in April.
"Several organizational changes took place while the Tenth Battalion was on Salisbury Plain. One of these involved the formation of a machine-gun section. Each battalion in the Canadian contingent was issued four American-made Colt(s)....
"The Battalion was also organized into four companies, but it was a convoluted process. The entire Canadian contingent had come to England in eight-company battalions. On 1 November they "reverted" (sic) to four companies, but this was over-turned later in the month by the War Office, which decreed that all British battalions must have eight companies. Unable to make up its mind, the War Office reversed itself in December, and the battalions had no sooner switched to four companies that they were once again ordered to restore the eight-company organization. The final decision was made in January 1915 in favour of four companies, designated by the letters A, B, C, and D. The Tenth was ordered to reorganize on this basis on 18 January and completed the change on the twenty-first"
It always gives me great pleasure to discover that some things never change.
For backdrop, prior to January 1915 the Old Contemptibles, the regulars, had engaged in the Retreat from Mons, the Battle of the Frontiers, the Race to the Sea and the First Battle of Ypres. There wasn't much of the old army left.
Edit: Another way of looking at it - November 1914 to January 1915 was the transition from the Cavalry led war of manoeuvre to the three year siege led, as usual, by engineers, artillery and the Forlorn Hope of the infantry.