III. Remarks on the cloaca and on the copulatory organs of the amniota

Abstract

The sphincter muscles of the anus of Crocodilia are differentiations of the postpelvic portion of the system of the m. rectus abdominis rather than of the true eaudal muscles. The copulatory muscles of the Carinatæ are derived from the m. sphincter ani solely, whilst in the Ratitæ they are also differentiations of muscles which are still attached to the pelvis, and are, therefore, skeleto-genital. The mammalian sphincter ani does not take a share in the muscle supply of the copulatory organ, and thus exhibits a difference from Birds and Lizards.