There is no suggestion that Darwin was a vegetarian - though unfortunately he appears on lists of 'famous vegetarians' on various websites. The notes below might help to clarify the confusion:

from 'Omniverous or Vegetarian? what famous naturalist think about it' by Professor Luis Vallejo Rodríguez, Spain, 1996:

. . . Of course, the most famous of all British naturalists also agreed with the other naturalists. I am referring to Charles Darwin (1800-1882) who at the age of 22 years started on a journey around the world which lasted 5 years. On this journey Darwin collected material which served to publish his most famous book in 1859: The Origin of Species by Natural Selection: Darwin was a member of the Royal Society of London and after his death he was buried in Westminster Abbey with great funeral honours and diplomatic representatives from many great nations were present at his funeral. Darwin wrote:

"The grading of forms, organic functions, customs and diets showed in an evident way that the normal food of man is vegetable like the anthropoids and apes and that our canine teeth are less developed than theirs and that we are not destined to compete with wild beasts or carnivorous animals."

"Although we know nothing for certain about the time or place that man shed the thick hair that covered him, with much probability of being right we could say that he must have lived in a warm country where conditions were favourable to the frugivorous way of life which, to judge from analogies, must have been the way man lived."

From an article in the Souvenir book of the 1957 IVU Congress in India:

All these examples show us that the common and persistent fallacy that one must eat flesh in order to be strong has no foundation in fact; indeed the exact contrary is true, Charles Darwin remarked in one of his letters: "The most extraordinary workers I ever saw, the labourers in the mines of Chili, live exclusively on vegetable food, including many seeds of leguminous plants." Of the same miners Sri Francis Head writes: "It is usual for the copper miners of Central Chilli to carry loads of ore of two hundred pounds weight up eighty perpendicular yards twelve times a day; and their diet is entirely vegetarian - a breakfast of figs and small loaves of bread, a dinner of boiled beans, and a supper of roasted wheat."

other quotes of unknown sources:

We have seen that the senses and intuitions, the various emotions and faculties, such as love, memory, attention and curiosity, imitation, reason, etc., of which man boasts, may be found in an incipient, or even sometimes in a well-developed condition, in the lower animals.

There is no fundamental difference between man and the higher mammals in their mental faculties ... The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind.

The love for all living creatures is the most noble attribute of man.