If you do it with an indexed mutual fund, you'll buy units of a mutual fund that holds all, or almost all, of the investments in a particular index. (moneysense.ca)
And any time you sell units of a mutual fund trust for more than you paid, you'll incur a taxable capital gain. (moneysense.ca)
In theory, mutual funds can split their unit prices, however since investors can buy partial units of mutual funds, there isn't really any point in doing so. (abcsofinvesting.net)