408 ELMER L. SHAFFER. 



is present an unpaired sex element (Figs. I and 2). One pair of 

 the complex is strikingly larger than the rest, being in the form 

 of somewhat curved rods (Text-fig, i). This pair corresponds 

 to the " macrochromosome " pair described by Kornhauser ('14) 

 in Enchenopa. 



Two other chromosome pairs (BB, CC, Text-fig, i) can also 

 be distinguished from the other chromosomes by their size, 

 being approximately half the size of the macro-chromosomes 

 (A A). The other 13 chromosomes show no size differences 

 which would enable us to arrange them in pairs or distinguish 



TEXT-FIG, i. Spermatogonial chromosomes, showing the relative sizes of the 

 chromosomes; the macrochromosome pair, A A, the BB and CC pairs, and 13 

 other chromosomes which show no size differences. 



them from each other. However, as will be later shown, the 

 AA, BB, and CC chromosome pairs are so characteristic in their 

 form and size that they can be recognized in all the diploid 

 groups. The size relations of the chromosomes of Cicada corre- 

 spond to those described by Kornhauser ('14) in Enchenopa. 

 Also in the Cercopidce (Homoptera), Boring ('13) has described 

 three pairs of chromosomes (A, B, C) which bear similar size 

 relations to the three pairs here described in Cicada. 



The sex-chromosome cannot be identified in the spermatogonial 

 groups either by its size nor by any peculiarities in its staining 

 reactions. In the resting spermatogonia there is, however, 

 always present a single chromatin nucleolus (Fig. 13) which 

 probably is the persisting sex chromosome. 



(b) Ovarian Follicle Cells. Among the follicle-cells of the 

 ovary, mitotic figures are very abundant. I have found a great 

 many mitoses not only among the follicle-cells surrounding the 

 young growing oocytes, but even among the follicle-cells sur- 

 rounding the almost mature oocytes. I have searched for evi- 

 dences of amitotic division among these cells, which has often 



