The Same, Questions, Book XXXV. What a father gives to his son after he has returned from the army does not form part of his castrense peculium, but belongs to another peculium, just as if his son had never been in military service. 1If a father should promise his son by a stipulation that whatever he acquires will be for the benefit of his peculium castrense, the stipulation will stand; but it will be void under any other circumstances. 2When a father stipulates with his son for his own benefit, the same distinction shall be observed. 3If a slave, forming part of the peculium of the son, should stipulate for or receive by delivery anything from a stranger, the property will belong to the son, without making any distinction between the considerations for the stipulation or the delivery. For, as the son sustains the double part of the head of a household and a son under paternal control, so the slave, who forms part of the peculium castrense, and who, under no circumstances, is subject to the authority of the father as long as the son lives, cannot acquire for the benefit of the father what he has merely stipulated for, or has received. Hence, if a slave, who belongs to the son, stipulates for anything, or receives anything from the father, the property delivered or stipulated for is acquired for the son, just as if the contract had been made with a stranger, since the person who stipulates or receives is such that the transaction is carried on for the benefit of the son, no matter what the consideration may be. 4If a father has lost the usufruct of a slave, the ownership of whom formed part of the castrense peculium of the son, the latter will have the entire ownership of the slave.