^ Nathaniel McConaghy (1993). Sexual Behavior: Problems and Management. Springer Science & Business Media. p. 186. ISBN 978-0306441776. Archived from the original on May 6, 2018. Retrieved March 25, 2018. In homosexual relations, most men do not reach orgasm in receptive anal intercourse, and a number report not reaching orgasm by any method in many of their sexual relationships, which they nevertheless enjoy.
15. “Personally, I don’t understand some peoples’ obsession, when there’s a perfectly good vagina right next door. Only a few GFs over my long and varied love life were into it, and for them it was like an occasional naughty treat. On these occasions there’s an extra hotness factor added in mentally. As for the raw physical characteristics of tightness and friction, vaginal is better in the long run. I once had a GF who was down for it any time, and we both got bored of it really quickly TBH. On the other hand, a different GF had done some rotten things and we broke up; while making up months later we were in bed spooning naked when suddenly her ass cheeks then asshole started gobbling my cock like Pac-Man, a one-off event that was hotter than molten tungsten.”
In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first (proto– meaning "first") and the anus was formed later at the opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the dent close up in the middle, leaving openings at the ends which become the mouth and anus.