THE GERM-CELLS OF CICADA (TIBICEN) SEPTEMDECIM. 405 



A. INTRODUCTION. 



The study presented here was done at Princeton University 

 during the last year. The material was collected during the 

 appearance of the ly-year locust (Cicada septemdecim) in the 

 vicinity of Princeton, N. J., during the spring of 1919 at the 

 suggestion of Professor E. G. Conklin. With such an interesting 

 life cycle as these insects have, it was thought that a cytological 

 study of their germ cells might reveal some important facts in 

 the history of the mitochondria and the chromosomes. Both 

 of these are constant and important structures of all cells, and 

 it is the opinion of the writer that no cytological study can be 

 complete which neglects either one or the other. It is only by a 

 correlated study of cytoplasmic and nuclear structures that we 

 can ever hope to solve the many perplexing questions in cell 

 economy. We use the almost mystic phrase: "interaction 

 between nucleus and cytoplasm" in many cases to cover our 

 ignorance concerning certain cell activities, but we are far from 

 knowing any of the specific actions and reactions between the 

 nucleus and cytoplasm. W T ithin recent years the study of mito- 

 chondria of animal and plant cells has attracted many workers, 

 with the result that many cytologists have come to regard these 

 structures as of vital importance in cell activities. Attention, 

 which for many years has been centered on the nuclear activities, 

 has been drawn to a more intensive study of the cytoplasm and 

 its structures. All these studies have emphasized the importance 

 of such structures as mitochondria in relation to cell metabolism. 

 Moreover, although the chromosome hypothesis of heredity 

 seems to be firmly supported by a vast amount of evidence, yet 

 one group of cytologists (Meves, Benda, Duesberg, etc.) maintain 

 that the mitochondria also have a role as the bearers of hereditary 

 characters. While the evidence which these workers have 

 gathered is not of a convincing nature, nevertheless the facts are 

 worthy of careful consideration. There are some reasons for 

 believing that inheritance in some cases is through the cytoplasm, 

 and we must not loose sight of the fact that "cytoplasm as well 

 as nucleus is concerned in heredity and differentiation" (Conklin, 

 '16). However, whether or not such cytoplasmic structures as 



