There occur as parasites on and within the bodies of fishes certain vesicular, usually caudate, bodies, termed Psorospermioe, the exact nature of which is very problematical. According to Lieberkuhn they occasionally give origin to amoebiform bodies, similar to those which are liberated from the pseudonavicellae of Gregarinida. In this case they should probably be regarded as the embryonic forms of some Gregarina. By Balbiani, however, they are looked upon as properly belonging to the vegetable kingdom.