After a third round of cell division, the two progeny of cell I as well as a second cluster of cells (II) start to express slouch. More cells express slouch in thoracic and labial segments than in abdominal segments. These cells are at the tips of parasegmental bulges in the mesoderm, corresponding to a posterior position at the parasegmental borders. Type I cells are close to the anterior borders. Soon after the above activity, an additional pair of mesodermal cells (III) express slouch. These type III cells are located in a lateral position at the parasegmental border, and found only in abdominal segments (Carmena, 1995).