On the composition and variations of the pelvic plexus in Acanthias vulguris

Whilst recently engaged upon the development of the pelvic plexus in Mustelus Iœvis I was much struck with the amount of variation in the number and position of the nerves forming it. This led me at the time to examine all the material which I was able to procure, and the results obtained have been given in a previous paper (12, 1900). Believing, however, that, in Bateson’s words, “the facts of variation must be the test of phylogenetic possibility” (4, p. 30), I determined to examine a still larger number of specimens of some other species of shark.