sentences:  As the students approached the rain-fed pond, they noticed that a large number of the northern leopard frogs (rana pipiens) had deformities, such as missing legs, extra legs, and other disfigurements.Concerned about the possibility that the deformities occurred because of a contaminant in the water, Ms. Reinitz contacted the Minnesota Pollution Control Agency (MPCA).As the MPCA did not have an amphibian specialist at the time, Reinitz was referred to the MPCA's invertebrate researcher, Dr. Judy Helgen.