Fig. 4. Collage of micrographs showing a complete cross section of a jellyfish. Micrographs were taken using a video capture system and a 25x objective on an interference contrast microscope. Fibres can be traced from the inner edge of the exumbrellar epidermis to the gastrodermal lamella. Note the high degree of branching of the fibres at their ends, and the intertwining of the fibres with the tissue of the exumbrellar epithelium and the gastrodermal lamella. Also note the coiled, slack appearance of the fibres in the medial half of the bell mesoglea and the absence of organisation in the fibres of the joint mesoglea. The black rimmed circular structures in the micrographs are air bubbles introduced during the thawing and transfer of the sample from the microtome to a microscope slide. (Inset) Tracings of the six fibres from gastrodermal lamella to exumbrella. Air bubbles are shown for orientation. The path lengths of the tracings were calculated, and a correction (described in text) applied to derive a reasonable minimum estimate of the unstressed length of the fibres. Note that the tracings follow a single branch of the fibre in the highly branched region near the gastrodermal lamella.