Figure 5.

Corresponding SEM and DIC images of stage 1 to stage 4 buds of T. wilhelma A1 - D1. SEM images of median section planes of the four bud stages of T. wilhelma, Framed areas are represented in A2 - D2 (SEM) and the DIC microimages of corresponding semi-thin sections in A3 - D3. In stage 1 buds (A) cells are densely packed and evenly distributed. Stage 2 buds (B) display early developing cortex (dco) and choanoderm (dcd) regions as well as few numbers of primordial choanocytes (pc) and megasclere bundles (msb). Developing lacunar system cavities (dlsc) are found in stage 3 (C) as separated developing choanoderm and cortex regions. In stage 4 (D) clearly developed lacunar system cavities (lsc), choanocyte chambers (cc) and distinguished cortex (co) and choanoderm (cd) are present.