The following attentions have been especially paid for the systematic characters of the cottoid fish.
(a) form and position of all fins.
(b) presence or absence of the ventral fin.
(c) changing of the form of the fins by growth.
These items are newly introduced for the systematic purpose of cottoid fish.
The results are summarized as follows:
(1) the parallelisms in the specializations among the forms of dorsal, pectoral and ventral fins are found.
(2) The form of the fins in the larval stages givas suggestions regarding the phylogeny.
