122 
Alice M. Boriiig 
Observations. 
Frequency. 
Although a large mimber of investigators have worked on 
Ascaris^ the small chromosome has beeil nieutioued by but two, 
Herla ('94) and Boveri ('99). In order te decide wlietlier it is a 
definite niorpbological element and has a definite fiinction, it is of 
first iinportance to know in what propoi*tion of wornis it is foiind 
and in what proportion of the eggs of each worin. 
In the present investigation, it was found in varj ing proportions 
in the eggs of thirteen of the eighteen worms studied. The frequency 
is iniich more striking in hivalens than in imüalens^ as out of the 
twelve biralens worms studied, there were only two with no small 
chromosomes. In uniralens, it is very rare. Three worms had none 
and the other three had it in only one or two eggs. 
In the thirteen worms in which it was found, the small chromo- 
some did not always appear in the same proportion of the eggs. In 
unixalens^ it was at first not found at all, but later after a carefiil 
search through many preparations, it was found in five eggs comiug 
from three different worms. In biralens^ the perceut of eggs froni 
one worm containing the small chromosome may be as high as 54, 
or as low as 5. In the cases counted they were 54 ^ , 44 % , 28 ^ , 
25^, 17^,5^. These percents were calculated from cases where 
a cousiderable number of equatorial plates were studied, as the 
following figiires show; 
Eggs with a small chromosome 12 (iO 22 11 4 2 
Eggs withoiit a small chromosome 10 75 56 32 19 40’ 
The possibilit}’ that the small chromosome might have some- 
thiug to do with sex determinatiou, made it seem worth while in 
this Connection to determine the ratio of males to females in As- 
caris megalocephala. I state here the numbers counted in case 
they may sometime be of use to other investigators. 
Males _ 1_175_16_8_13_4_10_1_1 
Females ~ 1 ~ 194 “ 23 ~ 12 “ 2l ~ 1 ~ 24 ~ 35 “ 37 ’ 
To compare with the frequency of the small chromosome, these ratios 
must also be stated in percents, as follows: 50^, 47^, 41^, 40_%i, 
38^, 36X, 29^, 3^, 3^. The case with 175 males to 194 fe- 
