CCP 4656     

Art. 4656.  Each defendant both plaintiff and defendant; no responsive pleadings to answer; no default required

Each defendant in a concursus proceeding is considered as being both a plaintiff and a defendant with respect to all other parties.  No exceptions or responsive pleadings may be filed to the answer of a defendant, and every fact alleged therein is considered as denied or avoided by effect of law as to all other parties.  If a defendant fails to answer, issue need not be joined by default.