92 THE EVOLUTION THEORY 



tion of numerous cases, whether some abnormal peculiarity in the 

 constitution of the germ-plasm in these eggs was not the true cause. 

 Hitherto, unfortunately, I have not been able to procure the fresh 

 material necessary to decide this point ^. From all this it must be 

 evident that we are not justified in regarding either the absence 

 of wings or the degeneration of the ovaries as a direct result of 

 the inferior nourishment supplied to the workers in the larval state : 

 but should any one still have doubt on this point I may mention that, 

 among our indigenous ants, there are two species in which the workers 

 are just as large as the fertile females, and that in tropical America 

 a species (Myrmecocystus megalocola) occurs in which the workers 

 are larger than the true females ; this must mean that they have 

 received more food than the females, though perhaps not the same 

 mixture of food. 



From all the facts we have discussed we can confidently conclude 

 that the differences in structure, which distinguish the workers from 

 the true females, do not depend upon the influence, in the individual 

 lifetime, of a poorer diet, but upon variation in the primary con- 

 stituents of the germ ; we must conceive of the germ-plasm of ants 

 as containing, in addition to male and female ids, special ids of 

 workers, in which the determinants of wing and ovary are degenerate 

 in some degree, while the determinants of other parts, such as the 

 brain, are more highly developed. The manner of feeding, however, 

 and perhaps the mingling with the food of a special secretion of the 

 salivary glands, acts as a stimulus which determines whether one 

 kind of id or another is to be liberated, that is, to become active and 

 to enter on the path of development. 



A proof of this view is to be found, it seems to me, in the 

 existence of transition forms between workers and true females, 

 which was first brought to general knowledge by Forel. Perhaps 

 it would be better to call these 'mongrel forms,' for their various 

 parts do not maintain a medium between the two types, but many 

 parts follow the type of the worker, and others that of the true 

 female. Thus Forel twice found a nest of the red wood-ant which 

 contained a large number of these mixed forms, all of which possessed 

 the small head and large curved thorax of the queen, but otherwise 

 resembled the workers in size and appearance, and also in the 



' Since completing my manuscript I note that the point was settled three years 

 ago, when Koshewnikow had the opportunity of investigating drone-pupae which were 

 abnormally reared in royal cells, and therefore fed with royal food. He found their 

 sexual organs perfectly normal, and agrees with me that the abnormalities in Vom Rath's 

 case must have been due to some other cause. (See the report by Von Adelung on the 

 Russian paper in Zool. CentralUatt, Sept. lo, 1901.) 



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