  We derive the structure, distribution of MS and PMS stars and dynamical state
of the young open cluster NGC 4755. We explore the possibility that, at the
cluster age, some MS and PMS stars still present infrared excesses related to
dust envelopes and proto-planetary discs. The radial density profile follows
King's law with a core radius $\rm\rc=0.7\pm0.1 pc$ and a limiting radius
$\rm\rl=6.9\pm0.1 pc$; the cluster age is $\rm14\pm2 Myr$. Field-star
decontamination reveals a low-MS limit at $\rm\approx1.4 \ms$. The core MF
($\chi=0.94\pm0.16$) is flatter than the halo's ($\chi=1.58\pm0.11$). NGC 4755
contains $\rm\sim285$ candidate PMS stars of age $\rm\sim1 - 15 Myr$, and a few
evolved stars. The mass locked up in PMS, MS and evolved stars amounts to
$\rm\sim1150 \ms$. Proper motions show that \ks-excess MS and PMS stars are
cluster members. \ks-excess fractions in PMS and MS stars are $\rm5.4\pm2.1%$
and $\rm3.9\pm1.5%$ respectively, consistent with the cluster age. The core is
deficient in PMS stars, as compared with MS ones. NGC 4755 hosts binaries in
the halo but they are scarce in the core. Compared to open clusters in
different dynamical states studied with similar methods, NGC 4755 fits
relations involving structural and dynamical parameters in the expected locus
for its age and mass. On the other hand, the flatter core MF probably
originates from primordial processes related to parent molecular cloud
fragmentation and mass segregation over $\rm\sim14 Myr$. Star formation in NGC
4755 began $\rm\approx14 Myr$ ago and proceeded for about the same length of
time. Detection of \ks-excess emission in member MS stars suggests that some
circumstellar dust discs survived for $\rm\sim10^7 yr$, occurring both in some
MS and PMS stars for the age and spread observed in NGC 4755.
