original description(ofDistoma proliferum Oka, 1933)Oka, A. (1933). Ein fall von kolonialknospung bei einer Synascidie. <em>Proc. Imp. Acad.</em> 9(8): 436-438.[details]
original description(ofPolycitor mutabilis Oka, 1942)Oka, A. (1942). On a new species of Polycitor from Japan, with some remarks on its mode of budding. <em>Annot. Zool. Japon.</em> 21(3): 155-162.[details]