Four Kinds of Generation

"Sariputta, there are these four kinds of generation. What are the four? Egg-born generation, womb-born generation, moisture-born generation and spontaneous generation.

"What is egg-born generation? There are these beings born by breaking out of the shell of an egg; this is called egg-born generation. What is womb-born generation? There are these beings born by breaking out from the caul; this is called womb-born generation. What is moisture-born generation? There are these beings born in a rotten fish, in a rotten corpse, in rotten dough, in a cesspit, or in a sewer; this is called moisture-born generation. What is spontaneous generation? There are gods and denizens of hell and certain human beings and some beings in the lower worlds; this is called spontaneous generation. These are the four kinds of generation.

The source for the above material:
MN 12 Maha-sihanada Sutta The Great Discourse on the Lion's Roar Translated from the Pali by Ñanamoli Thera & Bhikkhu Bodhi PTS: M i 68 Source: From The Lion's Roar: Two Discourses of the Buddha , edited and revised by Bhikkhu Bodhi (Kandy: Buddhist Publication Society, 1993). Copyright © 1993 Buddhist Publication Society. Used with permission. Copyright © 1993 Buddhist Publication Society. Access to Insight edition © 1994 For free distribution. This work may be republished, reformatted, reprinted, and redistributed in any medium. It is the author's wish, however, that any such republication and redistribution be made available to the public on a free and unrestricted basis and that translations and other derivative works be clearly marked as such.