E. A. COOKAYNK 91 



1904, XI, Plate X, fig. 4. The right side is much smalKr lli;m the Ml 

 and the costa of the right forewiiig is abnormally curved. 



A phenomenon exactlj' comparable to heti'rochroism in tlu; Lepi- 

 doptera appeared a few times during the cour.se of Morgan's extensive 

 experiments with the Diptrron JJnisupliila ampehphiki. He obtained 

 new mutations which bred on Meudelian lines and showed the same 

 kind of sex-limited inheritance as occurs in man in the case of colour- 

 blindness. 



These mutations affected the size and shape of the wings and 

 were of three kinds, " rudimentary," " miniature," and " rudimentary- 

 miniature." 



In one instance an individual appeared with a normal long wing 

 on the left and a " miniature " wing on the right side, in another there 

 was a normal long wing on the right and a " rudimentary-miniature " 

 wing on the left, and in two cases the wing on one side was intermediate 

 and on the other " rudimentary." Descriptions and figures are given 

 by Morgan in the Zeitschr. f. Induki. Ab.stantni.. 1912, vii, p. .323. 



It is particularly interesting that the same Mendelian characters 

 have been shown segregated both with and without segregation of sex 

 characters into opposite halves of the body in the same species Acidalia 

 virgularia, and Aglia tau, and that heterochroism of almost identical 

 nature has occui'red in Anthrocera trifolii both without gynandro- 

 morphism and in conjunction with it. Heterochroism has also occurred 

 both with and without gynandromoi-phism in Psilura monaclm and ab. 

 eremita. 



Abnormalities occurring in uniovular (lioinogeneous) twins afford 

 parallels to one form of gynandroimirphisni, and to heterochmisin in the 

 Lepidoptera. 



It is well known that both members ot a pair of such twins are 

 usually alike in all respects, and that hereditary diseases affect both, as 

 one would naturally expect, .since they arise by separation of the first 

 two cleavage cells, each of which then develops into a complete indi- 

 vidual. In fact they are the product of the union of a single sperma- 

 tozoon with a single ovum. To illustrate this point I collected a number 

 of examples in man in the British Journal of Children's Diseases. 



The best known exception to this rule is the free-martin in the ox, 

 which affords a close parallel to the gynandromorphism of insects, in 

 which the secondary sexual characters of the two sexes are segregated 

 to the opposite halves of the body. Free-martins are of two kinds, male 

 and female. The male free-maitin of which a good many examples are 



