DEVELOPMENT OF THE ANTENNJi OF TERMITES. 241 



reduction in the number and also the degree of rigidity of 

 the wing-ribs, and, lastly, in the ontogeny of the spiracles. 



It is small wonder, then, that the antennee should specialise 

 along a similar route, and it is not too much to say that these 

 organs in the higher termites tend to depart less and less 

 from their larval condition. Inferentially the ancestral type 

 was a multi-jointed organ with a process of joint-multiplica- 

 tion which Avas indeterminate in the sense that it continued 

 until the general growth of the whole body had ceased. In 

 any given species the variation in the action of the reducing 

 factor on the ancestral tendency for an indeterminate number 

 of joints causes the variation observable in the number of 

 joints in the final form of the antenna. The flagellum of 

 every antenna is an arrested structure, wherein, however 

 regular and however small the quota of joints, extra elemental 

 joints are present in the formative zone when the joint- 

 multiplication subsides. 



The dwarfing of an individual has a considerable effect 

 upon the antenna, as then either fewer elements are present 

 or those present are expressed as fewer joints. Moreover, in 

 a given community, as the larger individuals of a caste tend 

 to have more joints in their antennse, nutrition seems to play 

 an important role in joint production — or, to be more precise, 

 in the development of articulations. 



Nanism. — The term " nanism " is used in a restricted sense 

 to signify the dwarfed condition of an assemblage of 

 soldiers and workers — the characteristic state of such incipient 

 and juvenile communities as I have examined. In any com- 

 munities embracing major and minor castes dwarfing prevails 

 to a marked degree, as the minors are little else than under- 

 sized or abridged forms of the majors. True, with a few 

 species there are somewhat radical distinctions, but these are 

 exceptional and offset by others where the members of a caste 

 intergrade in size and character from small to large. Hei-e 

 there may be a greater difference between the largest and the 

 smallest than exists in species where the cleavage is sharply 

 defined. Although it still remains to be proved for all 



