They are optionally vikāras of the Aindrāgna. Sometimes these two Sūtras are combined into one. The commentator, however, sees in the vā of aindrāgnavikārā vā a deeper meaning. Agnī-Shomau, he says, consists of four, Indrāgnī of three syllables. Therefore if the name of more than one deity consists of four syllables, it should be treated as a vikāra of the Agnīṣomīya, if of less than four syllables, as a vikāra of the Aindrāgna. An exception must be made in the case of the gods of the prakṛti, as, for instance, the Aindra puroḍāśa, the Saumya caru. The exception applies to cases where the offering in a vikṛti sacrifice is meant for the same principal deities as those of the prakṛti offering. For instance, in the Darśa-pūrṇamāsa Agni and Soma are the deities of the Agnīṣomīya, Indra and Agni of the Aindrāgna. If then in one of the secondary or vikṛti sacrifices there occurs an Aindra puroḍāśa, or a Saumya caru, then the Aindra puroḍāśa is treated as a vikāra of the Aindrāgna, the Saumya karu as a vikāra of the Agnīṣomīya. The Somendra caru also, as its principal deity is Soma, would follow the Agnīṣomīya, the Indrāsomīya puroḍāśa, as its principal deity is Indra, would follow the Aindrāgna. If there is sameness both in the offering and in the deity, then the offering prevails. If a caru for Prajāpati occurs in a vikṛti sacrifice, it would follow that, being offered to Prajāpati, it should be offered with murmuring, but, as it is a vegetable offering, it follows the norm of the puroḍāśa, though the puroḍāśa is intended for Agni. If there is contradiction with regard to the substance and the preparation of an offering, the substance prevails. A puroḍāśa may be made of vrīhi, rice, or of nīvāra, wild growing rice. The wild rice has to be pounded, but not the good rice. The preparation, however, has to yield in a vikṛti, the important point being the substance. If there is contradiction with regard to the substance, the object prevails. An example makes the meaning of this Sūtra quite clear. Generally the yūpa or sacrificial post for fastening sacrificial animals is made of Khadira wood. But if a post made of wood is not strong enough to hold the animal, then an iron post is to be used, the object being the fastening of the animal, while the material is of less consequence. In a Prakṛti sacrifice there is no Ūha, modification of the mantras. Certain mantras of the Veda have to be slightly altered, when their application varies. In the normal sacrifices, however, no such alteration takes place. In a Vikṛti sacrifice modification takes place, according to the sense, but not in an arthavāda. Some mantras remain the same in the Vikṛti as in the Prakṛti. Others have to be modified so as to be adapted to anything new that has to be. If, for instance, there is a Puroḍāśa for Agni in the Prakṛti, and in its place a Puroḍāśa for Sūrya in the Vikṛti, then we must place Sūrya instead of Agni in the dedicatory mantra. When we hear words referring to something else, that is arthavāda. Arthavāda is generally explained as anything occurring in the Brāhmaṇas which is not vidhi or command. Here, however, it refers to Mantras or passages recited at the sacrifice. We saw how such passages, if they referred to some part of the sacrifice, had to be modified under certain circumstances according to the sense. Here we are told that passages which do not refer to anything special in the sacrifice, are arthavāda and remain unmodified. All this is expressed by the words paravākyaśravaṇāt. Vākya stands for padāni, words, such as are used in the nivāpamantra, &c. Some of these words are called samavetārthāni, because they tell of something connected with the performance of the sacrifice, as, for instance, Agnaye juṣṭaṃ nirvapāmi, I offer what is acceptable to Agni; others are asamavetārthāni, as, for instance, Devasya tvā Savituḥ prasave. When such passages which are not connected with some sacrificial act occur (śravaṇāt), they naturally remain unaltered. If what is prescribed is absent, a substitute is to be taken according to similarity. Here we have no longer modification, but substitution (pratinidhi). In cases where anything special that has been prescribed is wanting, a substitute must be chosen, as similar as possible, and producing a similar effect. According to Maṇḍana's Trikāṇḍa, the degrees of similarity are to be determined in the following order: Kāryai rūpais tathā parṇaiḥ kṣīraiḥ puṣpaiḥ phalair api, Gandhai rasaiḥ sadṛg grāhyam pūrvālābhe param param. 'What is similar by effect, by shape, by leaves, by milk, by flowers, and by fruit, By smell, or by taste is to be taken one after the other, if the former cannot be found.' If there is nothing very like, something a little like may be substituted, only it must not be prohibited.