Page:The Zoologist, 4th series, vol 6 (1902).djvu/203



When we undertake the consideration of nauseous or offensive smells as means of protection in the animal world, we are able, in some degree, to leave the region of hypothesis which environed us when discussing the question of similarity in sensory impressions in animal vision, and to arrive at negative evidence as to the universality of the sensations of smell. This question becomes most important in estimating the amount of protection afforded to animals by the possession of nauseous or offensive odours. It is unnecessary to recapitulate the many instances already recorded of this protective factor in the struggle for existence. It will suffice to mention, as examples of the phenomena, the immunity from attack possessed by the evil-smelling Skunk (Mephitis mephitica) in the Mammalia, and by the Danainæ, Acræinæ, and Heliconinæ among butterflies, in the possession of malodorous juices that can be exuded from the body. It is more than probable that this offensive attribute is much more prevalent than at present recorded: at the same time, to prove its efficacy, it is necessary to also establish some standard of appreciative nastiness in the smell-impressions of the animal world. Some animals possess a musky odour, Zool. 4th ser. vol. VI., May, 1902.