78 ROBERT H. BOWEN. 



1. The nebenkern of the insect spermatic! is composed pri- 

 marily of two distinct substances a chromophobic ground-sub- 

 stance presumably equivalent to the medullary material (of like 

 staining behavior) in the original chondriosomes; and a chromo- 

 philic substance presumably equivalent to the peripheral material 

 in the original chondriosomes. 



2. The chromophilic substance is arranged in a variety of ways 

 producing the so-called nebenkern "patterns." 



3. These patterns are presumably of at least two types (i) 

 the "spireme" type characteristic of Lepidoptera, and (2) the 

 " plate-work " type characteristic of Hemiptera. 



4. The chromophilic substance eventually disappears appar- 

 ently by some process of condensation and solution. 



5. As the chromophilic substance disappears, a new substance, 

 possibly a differentiation product of the chromophilic material, 

 makes its appearance within the mass of chromophobic stuff. 



6. This new (central) substance forms a core for each of the 

 elongating halves of the nebenkern, and possibly is the source of 

 the bleb-like swellings later developed on the tail sheaths. 



LITERATURE CITED. 



Baumgartner, W. J. 



'02 Spermatid Transformations in Gryllus assimilis with Special Reference 



to the Nebenkern. Kansas Univ. Sci. Bull., Vol. i. 

 Boring, A. M. 



'07 A Study of the Spermatogenesis of Twenty-two Species of the Mem- 

 brae idee, Jassidce, Cercopida and Fulgorida-. Journ. Exp. Zool., Vol. 4. 

 Bowen, R. H. 



'19 New Methods for the Analysis of Cytoplasmic Structures. Proc. Soc. 



Exp. Biol. and Med., Vol. 17. 

 '20 Studies on Insect Spermatogenesis. I. The history of the Cytoplasmic 



Components of the Sperm in Hemiptera. BIOL. BULL., Vol. 39. 

 '22 Studies. II. The Components of the Spermatid and their Role in the 



Formation of the Sperm in Hemiptera. Jour. Morph. (In press). 

 Doncaster and Cannon. 



'20 On the Spermatogenesis of the Louse (Pcdicitlits corporis and P. 

 capitis}, with Some Observations on the Maturation of the Egg. 

 Quart. Jour. Mic. Sci., N. S., No. 253, Vol. 64. 

 Gatenby, J. B. 



'17 The Cytoplasmic Inclusions of the Germ Cells. Part I. Lepidoptera. 

 Quart. Jour. Mic. Sci:, N. S., No. 247, Vol. 62. 



