Six forms (5 of which are new) of echinactinomyxon and 5 new forms of the collective groups neoactinomyxum, aurantiactinomyxon, guyenotia, synactinomyxon, and antonactinomyxon of oligochaetes in Lake Sasajewun, Algonquin Park are described. Five forms of echinactinomyxon designated as echinactinomyxon 'A,' 'B,' 'C,' 'D,' and 'E,' a form of neoactinomyxum, and a form of aurantiactinomyxon were found in Limnodrilus hoffmeisteri. Echinactinomyxon on radiatum, a form of synactinomyxon, and a form of antonactinomyxon were recorded from Tubifex tubifex. A form of guyenotia was found in Lumbriculus variegatus. The sporoplasmic mass of these actinosporeans was released through the anterior end of the epispore. An increase in the number of germ cells was observed in the floating spore stage of all forms except echinactinomyxon 'C' and the form of antonactinomyxon.
