526 CAROLINE BURLING THOMPSON 



tract; the lack of the sterile worker caste found in the higher 

 termites the large brain and the nearness to fertility noted in 

 both male and female soldiers. 



Two views are held today as to the origin of these complexes 

 of characters that we call the castes. In Italy, the classic theory 

 of Grassi and Sandias ('93-' 94) — that the castes are the product 

 of their environment, the result of special feeding and the action 

 of protozoa — finds an ardent advocate in Dr. Carlo Jucci. Jucci 

 ('20-21) has made certain interesting experunents in cutting off 

 the wings of developing nymphs, and has analyzed the excretory 

 products of the different castes, and, in a preliminary note before 

 the Academy dei Lincei, claims to have demonstrated the exist- 

 ence of the particular diet by which caste production was brought 

 about by Professor Grassi in his experiments. 



The view that termite castes are hereditary, the product of 

 the germ plasm, found its first support in France from Prof. E. 

 Bugnion ('12-' 13), who advanced strong evidence drawn from 

 observations on the mushroom-feeding and other termites of Cey- 

 lon. In England, the morphological work of Dr. A. D. Imms 

 ('19) on the primitive genus Archotermopsis gives valuable evi- 

 dence which will be quoted more fully below. In America, support 

 for this view has come from the field observations and the breed- 

 ing experiments of Dr. T. E. Snyder ('15, '16), from Dr. Alfred 

 Emerson, whose work on South American termites is still unpub- 

 Ushed, and from the writer, whose opinions are based upon the 

 differentiations found in newly hatched termites, and morphologi- 

 cal data from the adult castes. Valuable indirect evidence is 

 derived from the studies of Dr. C. A. Kofoid and Miss Olive 

 Swezy on the protozoa of the intestinal tract of termites. Kofoid 

 and Swezy ('19) state that all the castes of T. angusticollis are 

 infested by protozoa, and in this connection it should be remem- 

 bered that Grassi's hypothesis postulates the absence of protozoa 

 in the reproductive forms, as the cause of their fertihty, and, 

 conversely, the presence of protozoa in the sterile workers and 

 soldiers only. 



The biologist who believes that termite castes are of heredi- 

 tary origin will next ask the mode of origin. 



