164 HAROLD HEATH. 



of the conditions obtaining under the old regime. It is accord- 

 ingly not difficult to imagine that during this transition period the 

 usual mode of feeding of certain individuals may be interfered 

 with and unusual structures result. 



In every case these unnatural types are imperfectly developed. 

 For example, the wings of the soldiers are, so far as my experi- 

 ence goes, of less than average size, being in all but two cases 

 less than the length of the abdomen. The reproductive organs 

 likewise are imperfect. In one specimen one half of the ovary 

 was partially functional, the other being in an abortive condition. 

 In two other examples there was an incomplete development of 

 both sides. The mandibles also are of less than average size 

 though within the range of variability which Dr. Desneux writes 

 me is extraordinarily great. 



While appearances suggest that these unusual individuals are 

 produced as a result of disturbed conditions, chiefly if not alto- 

 gether connected with the food and method of feeding, there is 

 no definite proof to show that such is actually the case. For 

 several years I have carried on feeding experiments in the hope 

 that some light might be shed on this important problem, but up 

 to the present time the results are purely negative. I have fed 

 hundreds of immature individuals, which had not undergone 

 more than two molts, entirely or in part upon material carefully 

 removed from the stomach of worker termites and in some in- 

 stances mixed with fragments of the salivary glands, but such a 

 diet is not perfect, or at all events the mode of feeding is too 

 crude, for the insects soon die and cleared mounts show the ali- 

 mentary canal to be practically empty. Older individuals live 

 for a longer time on such fare but finally they likewise grow 

 feeble and die. At other times I have fed young and old ter- 

 mites on proctodeal food but the results are never positive. 

 Again I have added to sawdust, upon which these insects thrive, 

 varying quantities of different salts, especially those used in ex- 

 periments on chemical fertilization, and in other cases have used 

 different acids of various strengths. In other experiments I have 

 mixed the fragmented wood with many substances, nutritious and 

 innutritious intended to disturb the nutritive processes in some 

 degree, but here too, the animal may flourish or starve yet other- 

 wise exhibit no unusual modifications. 



