Bhashya
अन्तरिक्षमेव ऋक् वायु साम इत्यादि पूर्ववत् ॥
In plain words
Intermediate space is the ṛk and wind is the sāman, exactly as explained before.
Close to the Sanskrit
The intermediate space indeed is the ṛk, wind is the sāman, and so forth, as before.