No. 612] GENESIS OF ORGANIZATION OF INSECT EGG 713 



at random, D. superba and D. projectans, and these char- 

 acters relate to ahnost every part of the body. Many 

 other differences would probably also be found between 

 the physiological processes and general activities of the 

 adults and between the morphological and physiological 

 characteristics of the embryos, larvae and pupae of the 

 two species if they were compared from these standpoints. 

 It has been sliown tli;it tlic fnctor for the clmi-ncter club 

 wing affects not only tlu^ cliaractci' that ^ivo this muta- 

 tion its name, l)iit also other characters, for e.\ami)le the 

 presence or absence of a pair of spines on the sides of the 

 thorax, these being always absent when the factor for 

 club wing is present.^^ It is possible that the combina- 

 tion of a number of such factors as that for club wing 

 would ultimately satisfy the re(iuirements of systematic 

 entomologists and tliat new -pecies could then l)e made \\p 

 in the laboratory. Such iimtatioiis might therefore l)e of 

 evolutionary value. If, however, these mutations fail to 

 furnish cliaracters of specific rank, oi- diai-actci's that 

 may lead to the formation of new species, we must con- 

 clude that they are not of evohitioiia r\ siuiiiticanee, and 

 look elsew]iei(> for the factors that are res])onsi})le for 

 specific charactei- and that may undergo changes which 

 lead to tran>iriutation. 



Factors of this xnt may lie in the chromosomes or in 

 the cytophism, hut the\- ai'e pi'ohahly the result- of inter- 

 action Ix'tween chromosomes and cytopIa>m. A> |iointed 

 out above, interaction of this sort has ahundant 0])portu- 

 nity to operate during the germ-cell cycle. The cytoplas- 

 mic differentiations resulting from the metabolic processes 

 that culminate in the formation of an egg ready to undergo 

 maturation ai-e vei'y striking in the case of insects, as in- 



chi-v>ome'!id he.-th's. and tli.Te mViu.- to he m. vali.l reason 

 whv the e-u> .)f tlu-e heethv- are .lifferent in their type 

 and comph'xitv of oru'anization. hoth morpholo-n,,! and 

 ].hvsioloiiical. fn-m th<.>e of I)rnsr,,,l,,h, for whih' we do 



