Sponge larvae posses cillia with unusual terminal expansions which are curled or biconcave in shape externally, as seen by scanning electron microscopy. Thin sections, passing through the point where the ciliary shaft enters the expanded area reveal the ciliary axoneme to be surrounded by many membranous folds, some of which are vesicular. The 'club footed' cilia occur in disparate groups of Demospongiae and most frequently, all larval cilia are of this type. There is no immediately obvious correlation between the type of movement displayed by the larvae and the occurrence of terminally expanded cilia.
Circulatory system.....circulates blood (a vital delivery system of oxygen) throughout the whole body when tissues need it the most and with a constant supply.
Gene expression is the process by which the instructions in our DNA are converted into a functional product, such as a protein. When the information stored in our DNA? is converted into instructions for making proteins? or other molecules, it is called gene expression
