INSECT SPERMATOGENESIS 605 



sections will, I think, make clear the nature of the processes at 

 work, and their extraordinary similarity to the conditions which 

 I have described fully in the hemipteran nehenkern. In the 

 first place, it is abundantly clear that a ' spireme ' is in these 

 stages an impossible interpretation. There is no conceivable 

 arrangement of a thread in the nebenkern which will produce 

 a regular bounding line in both long and cross-sections of the 

 chromophilic material. Such an appearance can only be pro- 

 duced by a continuous surface, which, in accordance with the 

 optical principles previously referred to, would, if of proper 

 thickness, produce the effect of a simple line or thread when 

 seen in optical section. In other words the chromophilic sub- 

 stance is arranged in a plate- work, exactly as it is in the 

 Hemiptera. This is further proved by the fact that the chromo- 

 philic material now stains with sufficient intensity to be visible 

 in surface views (fig. 4, for example), a result impossible with 

 an open thread formation. The cross-sections particularly 

 show that this plate-work is arranged as a series of concentric 

 shells in which, however, more or less extensive irregularities 

 occur. The longitudinal sections are not so satisfactory, since 

 the section is rarely exactly parallel to the long axis of the 

 nebenkern, and this, coupled with the irregularities in the 

 plate-work and the difficulty of differentiating the various 

 layers with equal clearness, makes the picture particularly 

 confusing in the earlier phases of elongation. 



This series of figures shows further that the chromophilic 

 substance is constantly diminishing in volume, with an increas- 

 ing simplification of its structural arrangements. Indeed, in 

 the later stages of condensation the cross-sections are especially 

 simple (figs. 47 a and 9 a and b), and exhibit in every particular 

 an exact parallelism with the same condensation steps in 

 Hemiptera. The final result of this process of condensation is 

 the complete disappearance of the chromophilic material, the 

 last stages in this process being shown in figs. 8, 14, and 13, 

 the last two being from the same cyst. The ultimate fate of the 

 chromophilic substance, and, indeed, all of the stages which 

 directly precede its complete disappearance are thus exactly 



NO. 264 T t 



