Theory:

     Unfortunately I could not accompany Grandfather on that trip, but he told me about it afterwards. A big black canvas kit-bag was provided for Toto. This, with some straw at the bottom, became his new abode. When the bag was closed, there was no escape. Toto could not get his hands through the opening, and the canvas was too strong for him to bite his way through. His efforts to get out only had the effect of making the bag roll about on the floor or occasionally jump into the air — an exhibition that attracted a curious crowd of onlookers on the Dehra Dun railway platform.
Explanation:
 
Toto joined the narrator's grandfather on his journey. Unfortunately, the narrator was unable to accompany his grandfather that day. Nonetheless, his grandfather explained what happened during the journey. The grandfather gave Toto a large canvas kit bag; the bag was black.

The kit-bag turned into a temporary home for Toto; it was arranged with straw in the bottom for the Toto to live. Grandfather closed the bag so that Toto would not escape from it as he was aware of Toto's naughty misbehaviour.

Toto couldn't get its hands outside as the bag was closed, and it couldn't tear or bite the bag because the fabric was so strong. Toto's constant attempts to get out of the bag resulted in the bag rolling on the floor and some times jumping into the air. Toto's attempts to get out of the bag were amusing and drew onlookers' attention on the Dehra Dun railway platform.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Unfortunately  Unluckily
2.
Canvas A piece of strong cloth
 3.
Onlookers
Spectators
4.
Occasionally Irregularly
5.
AbodeThe place where you live
Reference:
National Council of Educational Research and Training (2006). Moments. The Adventures of Toto – Ruskin Bond (pp. 7-10). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.