俱舍論記 1.230

1.230

「法種族義至是生本義」者，此下別釋界、有兩釋。此即初解、約因以釋。能生諸法、諸法生因。如人於其姓等生、以彼姓人名為種族、是生本義。如一山中金、銀等礦名金等族，是多法族說名多界。一身，謂一有情身。一相續，謂一期相續。或一身謂一期身，一相續謂一有情相續。有十八類諸法種族，名十八界。

"The meaning of a lineage of dharmas ... is the meaning of being the root of origination": below this, the dhātus are explained separately; there are two explanations. This is the first explanation, which explains them in terms of causes. They are capable of generating all dharmas, being the generative causes of all dharmas. Just as a human being is born within their family name and the like, and people of that family name are called a lineage (gotra), this is the meaning of being the root of origination. Just as the ores of gold, silver, and so forth in a single mountain are called the lineages (gotra) of gold and so on, so too a lineage of manifold dharmas is called manifold dhātus. "A single body" refers to the body of a single sentient being. "A single continuum" refers to the continuum of a single lifetime. Or "a single body" refers to the body of a single lifetime, and "a single continuum" refers to the continuum of a single sentient being. There are eighteen classes of lineages of dharmas, which are called the eighteen dhātus.