102 CAROLINE BUELIXG THOMPSON 



lecting the somewhat older n^^nphs that are distinguishable 

 one from another, the different castes are alwaj's found mixed 

 together. 



2. It is stated that the diet of the newly hatched nymphs 

 may vary in quantity and in quality. Weismann's experiments 

 with the blow fly ('94) show that quantitative feeding produces 

 changes in stature that are not inherited: on the other hand, von 

 Ihering ('03) has shown that quahtative feeding is merely a 

 stimulus for rapid development. 



3. Even without the evidence of AVeismami, von Ihering, and 

 others, it is inconceivable that there coiild be a food powerful 

 enough to act selectively upon certain organs of the body, for 

 example, the brain and the sex organs, and produce types a? 

 diverse as the reproductive forms and the workers and soldiers. 

 It was this difficulty that led certain supporters of the food hy- 

 pothesis to assume the presence in a termite egg of the potential 

 structural 'tendencies' of aU the cUfferent castes, or of special 

 sensitive conditions of germ plasm, which were manifested only 

 by food, food therefore playing the role of the indirect rather 

 than the direct cause of differentiation. 



Xow, instead of assuming the presence of the characters of 

 all the different castes in a single egg, and in all eggs, how much 

 simpler is the assumption that there are chfferent kinds of eggs, 

 and that each egg contains the predetermined characters of a 

 single caste. With this assumption, the structural differentia- 

 tions of the various castes, or their protot}T)es, may be looked 

 for at the time of hatching. 



]My hope of finding internal structural differences in the newly 

 hatched njTnphs of L. fia\'ipes and L. virginicus has been very 

 satisfactorily realized, and these differentiations will form the 

 subject matter of the remainder of this paper. 



B. ZMATERIAL AXD METHODS 



^ly material was collected in the summer and autumn of 1916, 

 partly by the writer, partly by ^Ir. T. E. Snyder, of the Bureau 

 of Entomology of the U. S. Department of Agriculture, to whom 



