  In this paper we study in detail different types of topological solitons
which are possible in bilayer quantum Hall systems at filling fraction $\nu =1$
when spin degrees of freedom are included. Starting from a microscopic
Hamiltonian we derive an effective energy functional for studying such
excitations. The gauge invariance and $CP^{3}$ character of this energy
fuctional and their consequences are examined. Then we identify permissible
classes of finite energy solutions which are topologically non-trivial. We also
numerically evaulate a representative solution in which a pseudospin (layer
degrees of freedom) bimeron in a given spin component is intertwined with
spin-skyrmions in each layer, and and discuss whether it is energetically
favoured as the lowest lying excitation in such system with some numerical
results.
