66 Bulletin American Museum of Natural History. [Vol. XXIII, 



The various extracts above quoted show very clearly that previous 

 authors have been impressed by very different aspects of the complicated 

 phenomena of polymorphism, and that each author has emphasized the as- 

 pect which seemed the most promising from the standpoint of the general 

 evolutionary theory he happened to be defending. Escherich has recently 

 called attention to two very different ways of envisaging the problem; one 

 of these is physiological and ontogenetic, the other ethological and phylo- 

 genetic. As these furnish convenient captions under which to continue the 

 discussion of the subject, I shall adopt them, and conclude with a third, the 

 psychological aspect, which is certainly of sufficient importance to deserve 

 consideration. 



3. The Ontogenetic and Physiological Aspects of Polymorphism. 



While the ontogeny of nearly all animals is a repetition or reproduction 

 of the ontogeny of the parent, this is usually not the case in the social Hymen- 

 optera, since' the majority of the fertilized eggs do not give rise to queens 

 but to more or less aberrant organisms, the workers. And as these do not, 

 as a rule, reproduce, the whole phenomenon is calculated to arouse the 

 interest of both the physiologist and the embryologist. The former, con- 

 centrating his attention on the reactions of the animal to the stimuli 

 proceeding from its environment, is inclined to study its later stages as 

 determined by the reactions to such stimuli, without regard to any internal 

 or hereditary predetermination or disposition, while the embryologist seeks 

 out the earliest moment at which the organism may be shown to deviate 

 from the ontogenetic pattern of its parent. If this moment can be detected 

 very early in the development he will be inclined to project the morpholog- 

 ical differentiation back into the germ-plasm and to regard the efforts of 

 the physiologist as relatively unimportant if not altogether futile. Now 

 in his study of the social insects the embryologist is at a serious disadvantage, 

 since he is unable to distinguish any prospective worker or queen characters 

 in the eggs or even in the young larvae. Compelled, therefore, to restrict 

 his investigations to the older larvse, whose development as mere processes 

 of histogenesis and metamorphosis throws little or no light on the meaning 

 of polymorphism, he is bound to abdicate and leave the physiologist in 

 possession of the problem. 



nursing instincts which prevent the workers from appropriating much of the food supply of the 

 colony to their individual use. In many of the higher animals also (birds, mammals) reproduc- 

 tion is inhibited by the exercise of the nutricial function. A third method of inhibiting or de- 

 stroying the reproductive function is known to occur in the ' parasitic castration ' of certain bees 

 and wasps {Andrena, Polistcs) by Streiisiptera {Siylops. Xenos, etc.). See Perez, Des Effets du 

 Parasitisme des Stylops sur les Apiaires du Genre Andrena. Actes Soc. Linn. Bordeau., 1SS6, 

 40 pp 2 pU. Westwood (Notice of the Occurrence of a Strepsipterous Insect Parasitic on Ants, 

 discovered in Ceylon by J. Nietner, Trans. Ent. Soc. London (2), V, 1861, pp. 418-420) has also 

 described a Stre'psipteron (Myrmecolax nietneri) which in all probability produces this form of 

 castration in certain Formicidse. 



