494 T. H. MORGAN 
That an X chromosome may be present attached to another 
chromosome has been shown in recent years by Boveri, Boring 
and Gulick in several species of Ascaris. The same looseness 
of attachment that I have observed has also been found in the 
eggs of Ascaris where in certain individuals and at certain times 
a separation has been recorded, while in other individuals the X 
chromosome remains completely united with its larger compan- 
ion. In my own ease the attachment is between two X chromo- 
somes While in the other cases the attachment is between an X 
and what is apparently an ordinary chromosome. 
OTHER POSSIBLE INTERPRETATIONS CONSIDERED 
In my former paper when dealing with the differences in the 
chromosomal groups in the equatorial plates of the polar spindles 
of the male- and female-producing eggs I have suggested that 
the change could be accounted for if in the male egg the two small- 
est chromosomes (the two small x’s) each left its larger partner 
and fused together while the two larger also fused. This would 
give the same actual number as before, but a relative difference 
in size would result. The logical conclusion from the assumption 
would be that when the polar bodies are given off the large X’s 
separate (reduction division for the pair) and the small 2’s 
also separate, the other chromosomes dividing equationally. This 
assumption was necessary for the large X and the small x pair 
because in the spermatogenesis a large XY and a small 2 are still 
present. 
If this view were correct the lagging chromosomes in the ana- 
phase of the male egg should consist of a large and a small chro- 
mosome. The facts show that two chromosomes do actually 
lag but unfortunately for the assumption they are equal and rel- 
atively large. The doubleness of this lagging body can be better 
explained by a precocious division into equal parts, since the 
other chromosomes that pass out into the polar body also show 
signs of division at this time. It is clear that my former inter- 
pretation must be abandoned. 
There is another interpretation that might be considered, namely, 
that the lagging body is really a large X and small z closely united 
