58 ROBERT H. BOWEN. 



Platner ('89). Meves concluded that in the process of condensa- 

 tion, the constituent materials of the original mitochondrial vesi- 

 cles had simply exchanged places, the chromophilic substance 

 having run together to form a homogeneous, central core, for 

 which the formerly internal, chromophobic substance now acts 

 as an envelope. 



Gatenby's ('17) account 1 is much more complete and proves 

 conclusively that the details as given' by Meves are badly distorted 

 through the use of acetic acid in the fixative. Gatenby shows 

 that the running together of the mitochondrial vesicles occurs in a 

 rather orderly way, the chromophobic material gradually fusing 

 to form the main body of the nebenkern within which the chro- 

 mophilic substance is molded into a long, but perfect spireme 

 wound up, as it were, within the nebenkern proper. Omitting, 

 for the present, any discussion of details, it is clear that the ne- 

 benkern thus formed is not homogeneous, but quite the contrary, 

 the exact (apparent) pattern assumed being dependent on the 

 perfection of the technical treatment. The essential result has 

 been the fusion of the chromophobic material of the various 

 chondriosome spheres to form a continuous, homogeneous matrix 

 in which is embedded the chromophilic material at first in a fan- 

 tastic, thread-pattern. How is this result to be compared with 

 the nebenkern formed by the fusion of thread-like mitochondria? 



Since it has not been possible to differentiate the chromophobic 

 material in the thread-like mitochondria of the Hemiptera, one 

 can not trace the gradual evolution of the nebenkern as Gatenby 

 has done; although in preparations not too darkly stained one 

 sometimes gets the impression that the substance producing the 

 nebenkern is not as homogeneous as it often appears to be. Once 

 fully completed (perhaps even earlier), the nebenkern begins to 

 show the first clear signs of a differentiation into two substances. 

 This first makes itself evident by the appearance of a large num- 



i So far as I know, Gatenby's results have not yet received any confirmation 

 from other workers. It is, therefore, possible that with further study of the 

 nebenkern in Lepidoptera other interpretations of the " spireme " structure as 

 described by Gatenby will be suggested. However, for the purposes of. this 

 discussion, I have considered Gatenby's account as correct, and the conclusions 

 reached will not be affected in any important way should the details of the 

 " spireme " formation fail of substantiation. 



