abstracts: paleontology 229 



ENTOMOLOGY. — The question oj the phylo genetic origin of termite 

 castes. Caroline Burling Thompson and Thomas Elliott Sny- 

 der. Biol. Bull. 36: 115-129, 2 plates, 5 text figs. February, 

 1919. 



The recent observation of one of the authors, that the castes of ter- 

 mites are of germinal origin and not produced by environmental con- 

 ditions, leads to the question of the phylogenetic origin of these varia- 

 tions or castes. Are termite castes to be considered as fluctuating 

 variations or as mutations? 



Several lines of approach lead to this problem; the study of fossil 

 insects; the comparative morphology of termites; exact field observa- 

 tions on termite biology; breeding experiments to determine the type 

 of progeny and the results of hybridization. Although none of these 

 aspects have been exhaustively studied, there are some data, sum- 

 marized in this paper, drawn from the literature of social insects and 

 from the notes of the two authors. 



The morphological facts show that a gradation of characters may be 

 traced throughout the members (castes of a species, e. g., Reticulitermes 

 flavipes). These castes might be interpreted either as the gradations 

 in a series of fluctuating variations, or as a series of mutations formed 

 by loss. 



Field observations and breeding experiments seem to indicate that 

 although the "first form" reproductive individuals produce young 

 of all the castes, the "second" and "third form" individuals breed 

 true to their own fertile castes. In some breeding experiments in arti- 

 ficial nests, from parent reproductive individuals of the "second 

 form" no fertile individuals of any kind were produced. 



The authors intend to undertake a series of studies and experiments 

 upon the morphology and the breeding of the termite castes. C. B. T. 



FALUONTOhOGY.— Appendages of trilobites. Charles D. Walcott. 

 Smiths. Misc. Coll. 67: No. 4, Cambrian Geol. and Pal. IV. 115-216, 

 pis. 14-42, text figs. 1-3. December, 1918. 



In this recent paper Dr. Charles D. Walcott summarizes his in- 

 vestigations of the appendages of trilobites during the past forty- 

 five years, a research undertaken in pursuance of a promise made to 

 Professor Louis Agassiz in 1873. Since that time, he writes, "I have 

 examined and studied all the trilobites that were available for evidence 

 bearing on their structure and organization." 



