The yuvan is optionally spoken of as gotra when contemptuous reference to him is intended.,
Thus गार्ग्यो जाल्मः or गार्ग्यायणो जाल्मः ॥ When contempt is not intended, the only form is गार्ग्यायणः ॥ This is also a Vartika and not a sutra.,
यूनश् च कुत्सायाम्
Adhyāya 4 · Pāda 1 · Rule 167