Oscar Wilde, The Picture of Dorian Gray: "I wonder will you understand me?"

In The Picture of Dorian Gray, I came across the following passage, spoken by Basil Hallward:

There is nothing that art cannot express, and I know that the work I have done since I met Dorian Gray is good work, is the best work of my life. But in some curious way — I wonder will you understand me? — his personality has suggested to me an entirely new manner in art, an entirely new mode of style.

I fail to understand the lack of a comma separating I wonder and will you understand me. Doesn't it make it sound somewhat awkward? Or is it part of Wilde's style? Or perhaps simply a printing error, which survived through successive editions?

Googling the sentence only returns pages quoting The Picture of Dorian Gray, hence bringing little information.

Can someone explain this to me?

This is a case where punctuation conventions have changed since Wilde’s time.

In standard modern prose, it does indeed require a comma. Certain forms of phrase can come after wonder without a comma:

I wonder whether it will rain today?

I wonder where my water buffalo is?

However, if the phrase after wonder is a standalone question, a comma is required:

I wonder, will it rain today?

I wonder, where is my water buffalo?

In Wilde’s time, though, it was quite usual to write this latter form without a comma.

Browsing Google books results for "I wonder will you" corroborates this: the 19th-century hits tend to lack commas, but examples from the mid-20th-century on almost all have the comma (except for a few in poems with other non-standard punctuation).