、、、。
'That' only has two cases — nominative and accusative — and doesn't change form based on case.
Literal
'That' [locative-には], nominative-case, accusative-case [possessive-の] two [only-しかなく], case [according to-による] form [possessive-の] change [topic-は] not-exist.
A meta-linguistic sentence about English grammar. Notice how the linguistic terminology uses native Japanese compounds: 主格 (nominative), 目的格 (accusative), 格 (grammatical case). しかない means 'only' with an emphatic negative frame — 'there exist only X, no more' — and the continuative しかなく threads the clause into the next. The noun phrase 格による形の変化 ('form change according to case') is a very nominal-heavy Japanese construction typical of academic writing.