Yes - Stephen is the moocow. In the first section of the first chapter, we get the first glimpse of Stephen's observation. The narrator says "he was baby tuckoo" meaning that his father always told him that he was baby tuckoo. This is a very basic illustration of what Stephen remembers as a little boy. Think of your first memories and how disjointed they are and you can kind of get the drift. At the end of the section on the second page of the novel, Stephen is hiding under the table because he apparently told his neighbor Eileen (who is Protestant - Stephen is Catholic) that he would marry her when he grew up. As such, he is told that he will apologize or else an eagle will come and pull out his eyes. These are all first memories of Stephen's.