96 CAROLINE BURLING THOMPSON 



Dewitz (78) writing of the postembryonic development in 

 insects, thinks it highly improbable that the workers can affect 

 the eggs and the young by treatment, such as warmth, food, 

 licking. He considers that the great difference between queen 

 and worker ant could not have been caused by the care of the 

 adult workers, but that the eggs must be predetermined within 

 the body of the mother. 



In the case of termites Dewitz finds it hard to believe that 

 the workers can exert any influence upon the young 'larvae,' 

 since the latter can get their own food. He concludes that, in 

 spite of the similarity of the young 'larvae,' the germ of the 

 future form, either winged or wingless, lies ready in the egg. 

 Referring to the work of Dzierzon, Dewitz ends with the remark: 

 "^Mochten recht bald zwei ahnhche Manner auftreten, welche 

 gleiches Licht iiber die Entwicklung der Ameisen und Termiten 

 verbreiteten." 



Herbst ('01) in a work entitled "Formative Reize in der thieris- 

 schen Ontogenese" devotes one section to the consideration of 

 "external formative (morphogenic) stimuli."' Beginning with 

 the developmental causes of the castes of social insects, he re- 

 ^^ews the work of Grassi and Sandias on termites, and remarks 

 that it must be recognized at once tliat there are many gaps in 

 our knowledge of caste differentiation. He points out that while 

 Grassi states that 'saliva' is the cause of differentiation in termites, 

 nothing is known about its nature except that it "e un liquido 

 incoloro spiccatamente alcalino e non continente alcun elemento 

 rilevabile al microscopio." After discussing Grassi's hypothesis 

 of the effect of saliva upon the parasitic protozoa and their 

 possible influence upon the sex organs, the question of the origin 

 of worker and soldier, and the production of the 'substitute' 

 royal forms, Herbst concludes with the words, 



Es dlirfte aus vorstehenden Erorterungen hervorgehen, dass unsere 

 Kenntnisse von den Bildungsursachen den verschiedenen Termiten- 

 kasten noch nicht gerade sehr tief gehen. 



Ha\'ing anah^zed the question of caste differentiation in the 

 social Hymenoptera, Herbst suggests that an internal secretion 



