REVIEWS. 927 
(ocellatus x populi), Saturnia (pavonia Xx pyri), and L[thysia (zonaria x 
hirtaria). 
GynanDRomorPHOUS MonGRELS. 
Here the case of the gynandromorphs produced by the crossing of 
Lymantria dispar with its var. japonica is considered. 
THEORETICAL EXPLANATION OF GYNANDROMORPHISM. 
All the theories are placed under four heads. 
(1.) Supposes that gynandromorphs are formed from (a) a fusion of 
two ova, or (b) from a binucleate ovum. 
(2.) That they are formed by an abnormally dividing single ovum. 
(3.) The Mendelian hypothesis based upon supposed differences in 
the potency of the sex characters in different races and species. 
(4.) That they are due to abnormal conditions occurring during the 
development of a normally fertilised ovum. 
The discussion of these explanations and the consideration of a large 
number of relative facts take up the remainder of the paper. 
CoNCLUSIONS. 
We have given these verbatim, as to condense them would only lead 
to misrepresentation. 
‘¢(1.) Gynandromorphs probably fall into three groups. The first 
two groups contain a majority of symmetrical gynandromorphs showing 
a blending or fine mosaic of male and female characters, and some 
showing characters predominantly male or female, but having on the 
wing streaks with the colour or pattern of the opposite sex. 
« These are unisexual or have sex glands containing mingled ovarian 
and testicular tissue. 
“The third group contains the completely and almost completely 
halved gynandromorphs, some with a coarse mosaic arrangement and 
some with a fine mosaic arrangement of sexual characters. 
“«(2.) The first group is due to a difference in the potency of the 
factors for sex, or secondary sex characters, or both, occurring in the 
two parents. The characters behave as simple Mendelian dominants 
and recessives, respectively. This difference occurs in Lymantria dispar 
and its var. japonica. 
‘< (3.)) The second group is probably due to a failure in the normal 
process of fusion of the sex chromosomes of the spermatozoon and ovum. 
This is especially lable to occur in the cases where the parents are of 
different species. 
“(4.) In the third group the condition is due to an irregular dis- 
tribution of the chromatin, which carries the factors for sex and for 
secondary sexual characters, or for one of these alone, to the first two 
cleavage cells. Thus it occurs at a late stage in mitosis and not at an 
early stage as in the first two groups, and the first two cleavage cells 
are different instead of being alike in their chomatin. 
“(5.) A similar, irregular distribution of the chromatin carrying a 
somatic character may take place, and this leads to heterochroism. 
“(6.) An irregular distribution of sex and somatic factors may 
occur together and this leads to the production of a heterochroic 
gynandromorph. 
“(7.) The existence of these strictly parallel groups of heterochroic 
insects, simple gynandromorphs, and heterochroic gynandromorphs, 
