Fig. 1. (A-D) Comparison of the pattern of invagination sites in the myriapod Glomeris marginata and the spider Cupiennius salei. Confocal micrographs of flat preparations of embryos stained with phalloidin-rhodamine. Anterior is towards the top, the midline towards the left. (A) Pattern of invagination sites in the opisthosoma of the spider. The invagination sites are arranged in seven rows consisting of four to five invagination sites each. The arrows point to two lateral anterior invagination sites that can be easily identified in each hemisegment. (B) A strikingly similar pattern and number of invagination sites is visible in the leg segments of the myriapod. As in the spider, the invagination sites form seven rows consisting of four to five invagination sites each. The arrows point to two lateral anterior invagination sites. (C) Higher magnification of an apical optical section of invagination sites in the ventral neuroectoderm of Glomeris. The arrowheads point to two invagination sites. (D) Basal optical section of the same region shown in C. Basally enlarged cells are visible (asterisks) underneath the dots of high phalloidin-rhodamine staining. o3 to o5, opisthosomal segments 3 to 5; l1 to l3, leg segments 1 to 3. Scale bars: 100 µm in A; 50 µm in B; 10 µm in C,D.