Complex sentence: After penetration, they transform to schistosomula (subadult stage) and look for peripheral nerves to use them to get to the spinal cord through which they continue their migration to the brain and, finally, the nasal tissue in a bill.
Split into simpler sentences: After penetration, they transform to schistosomula (subadult stage) and look for peripheral nerves to use them to get to the spinal cord. Through it they continue their migration to the brain and, finally, the nasal tissue in a bill.