72 Bulletin American Museum of Natural History. [Vol. XXIII, 



which are often cited as furnishing proof of this connection, are even more 

 compHcated and obscure than those of the social Hymenoptera. While 

 Grassi and Sandias/ and Silvestri,^ agree with Spencer in regarding the 

 feeding as the direct cause of the production of the various castes, Herbst,* 

 who has reviewed the work of the former authors, shows that their observa- 

 tions are by no means conclusive; and Heath'' makes the following state- 

 ment in regard to his experiments on Californian termites: "For months 

 I have fed a large number of termite colonies of all ages, with or without 

 royal pairs, on various kinds and amounts of food — proctodteal food 

 dissected from workers or in other cases from royal forms, stomodseal food 

 from the same sources, sawdust to which different nutritious ingredients 

 had been added — but in spite of all I cannot feel perfectly sure that I have 

 influenced in any unusual Avay the growth of a single individual." 



This rather unsatisfactory answer to the question as to whether quantity 

 or quality of food or both, have an ergatomorphic value, has led some in- 

 vestigators to seek a solution along more indirect lines. Thus O. Hertwig 

 and Herbst suggest that the morphogenic stimulus may be furnished by 

 some internal secretion of the reproductive organs. This, too, is possible,, 

 but owing to our very imperfect knowledge of the internal secretions, even 

 in the higher animals, we are not in a position either to accept or reject this 

 suggestion. 



More tangible is Emery's attempt ^ to explain the worker characters 

 as the result of a struggle among the parts of a prematurely metamorphosing^ 

 insect. He has not been led into the invisible battle of the ids and deter- 

 minants on which Weismann recently constructed his hypothesis of germinal 

 selection,® but is content with a struggle between the larger regions of the 

 body and between their various organs. This point of view was suggested 

 by his study of the mermithergates. He is of the opinion that " the same law 

 of growth which determines the proportions of the head and gaster in the 

 Mermis-infested workers (see pp. 24, 25 antea) obtains also in normal ants. 

 I designate it as the "law of opposition between head and gaster" and would 

 state it as follows : 



"While the imago is developing within the full-grown ant larva, what is 

 needful for the structures essential to the life of the organism is first empha- 

 sized, especially for the digestive and reproductive organs contained in the 

 gaster; the formation of the external shape of the head, and especially of 



1 Costituzione e Sviluppo della Societa dei Termitidi. Catania, 1893, 150 pp., 5 pll. 



2 Operai ginecoidi di Termes, con osservazioni intorno 1' origine delle varie caste nei Termi- 

 tidi, Real. Accad. Lincei. X, s6r. 5, 1901, pp. 479-484. 



3 Formative Reize in der Tierischen Ontogenese, Leipzig, Arthur Georgi, 1901, pp. 20-24, 



4 The Habits of Cahfornia Termites. Biol BuU. IV, Dec. 1902, pp. 62-23. 

 6 Zur Kenntniss des Polymorphismus, etc., loc. cit., p. 603. 



8 On Germinal Selection. Religion of Science Library. Open Court Publ. Co., Chicago, 

 1896. 



