The form in which the contract is made or the number of instruments in which its terms are to be sought, is not conclusive of the question of its entire or severable character. A contract which is found in one instrument or instruments executed at the same time, may nevertheless be severable.1 On the other hand, a contract the terms of which are to be sought in a number of different instruments, may be entire.2 It seems to be assumed that if a contract is contained in one instrument, it is prima facie an entire contract.3