There were many incarnations, and incarnations are coming incessantly just like there are waves in the ocean or in the river. You cannot sit down and count how many waves are flowing. As it is not possible, similarly, you cannot also count how many incarnations are there, how they are coming out. But the most important of them are described. And the conclusion is made that Krsna is the origin, as it is confirmed in the Bhagavad-gita. Aham sarvasya prabhavah. "I am the origin of everything, even the incarnations." Aham sarvasya prabhavo mattah sarvam pravartate [Bg. 10.8]. Everyone, all incarnations, all demigods, all living entities, all energies. The Vedanta-sutra also confirms, janmady asya yatah [SB 1.1.1]. The Absolute Truth is that which is the original source of everything.
Lecture on Srimad-Bhagavatam 1.3.29, Los Angeles, October 4, 1972