Some Details

Three ship's surgeons, opposite numbers of Dr McCoy:

in "Nor Iron Bars," Dr Hoyle on the Flyaway II to Alpha Centauri;

in "A Dusk of Idols," Dr Rosenbaum on an unnamed ship returning from the Heart stars;

in "And Some Were Savages," Dr Clyde Bixby on the UNSS Brock Chisholm.

Three references to Canes Venatici:

in "This Earth of Hours," the planet Calle orbits a star in the Canes Venatici cluster which, in this context, has to mean a star cluster in the Canes Venatici constellation, not a cluster of galaxies;

in "Beep"/The Quincunx Of Time, the planet Hathshepa orbits a star on the rim of the eleven light year distant galaxy NGC 4725 in the constellation of Canes Venatici;

in "A Style in Treason," there is an Emperor of Canes Venatici.

In its timeline, Calle is an outpost of the Central Empire of the galaxy, thus is not part of any cluster empire such as the one in "A Style in Treason." The galaxy of "A Style in Treason" is rich in empires since the Green Exarch "...drew tithes from six fallen empires older than man..." (Anywhen, New York, 1970, p. 19).

A Quincunx Of Ancient Trees

The characters in "Beep" by James Blish, living in our future, receive messages from several periods of their future. While Blish was expanding "Beep" into The Quincunx Of Time, he was also writing Midsummer Century (London, 1975). Thus, these works became connected.

Midsummer Century refers to "...a quincunx of ancient trees..." (p. 48).

Further, a message transmitted as a Dirac beep circa 25,000 AD in Midsummer Century is received in the Dirac beep in 2091 AD in Quincunx. The message is sent in this form:

"...so that all receivers [past, present or future] who might have any reason to care about the problem should have a record of it." (p. 86)

The receivers include the inventor of the Dirac transmitter, Thor Wald, a major character in Quincunx, referred to early in Midsummer Century, who draws inferences about the dimensional structure of time from:

a reference in this Dirac message to the projection to 25,000 of a personality originating in 1955;

a Dirac message, in both "Beep" and Quincunx, from a world-line cruiser traveling from 8873 to 8704 along the world-line of a planet in Canes Venatici.

This diptych is a worthy successor of HG Wells' The Time Machine. Blish said that readers of Midsummer Century would probably not realize that it had been written according to an old formula: the action must start in the here and now before quickly moving to an exotic location. Its hero, John Martels, the personality temporally transmitted to 25,000, begins his adventure in 1985 in a milieu of brain-drain, Pakistani immigrants, British "public" schools, new redbrick polytechnics, a class division between the two sides of a British bar, a First in astrophysics for a man with an "atrocious" working-class accent and a new radio telescope in an American University.

Like Wells' Time Traveler, Martels:

travels thousands of years into the future;
meets evolutionarily changed human beings in a paradisal environment;
spends some time in a museum.

Also like the Time Traveler, Wald expounds the theory of time as a fourth spatial dimension.

Just as we want to know when the Time Traveler went, we also want to know more about the futures disclosed in the Dirac beep.