A Small Chromosome in Ascaris niegalocephala. 
121 
As all the available material that might give a clue to its meaning 
has been carefully studied, the observations made are here described 
and a lew suggestions offered as to their possible meaning. 
I wish here to thank Prof. Boveri for all the courtesies extended 
t(» me in his laboratory, for his own personal interest in my work, 
and for liis many helpful suggestions. 
Material and Methods. 
Eggs froui eighteen worms, taken from twelve ditferent horses 
were studied. Of these worms, twelve were himlens and six uni- 
valens. It may here be mentioned that in tive cases, both hivaJms 
and univalens worms were found in the same horse. This fact 
shows that the worms which are found in a single host may some- 
times come from different parents. On the other hand, it is not im- 
possible, that all the worms in one horse may have a common hered- 
ity. Therefore, in order to study individuals which had the least 
possible relatiouship, it was important to take them from as many 
different horses as possible. 
Albumen fixative as used for paraffin sections, was smeared in 
a very thin layer on the slides, the eggs then spread in a single 
layer with a coverglass, and the albumen coagulated with a few^ 
drops of formalin. By this means the eggs were fixed firml}^ to the 
slide, but not injured. A thermostat at 37° C. was used to hasten 
the develoi)ment. It was found that when a few eggs on a slide 
had divided into two cells, the majority would have good first cleav- 
age equatorial i)lates. The eggs were fixed in acetic alcohol. (4 parts 
96^ alcohol to 1 part glacial acetic-acid), stained in alcoholic hy- 
drochloric-acid carmine, and mounted in glycerine. 
The chromosomes of the first cleavage were studied for the most 
part, but I made some preparations of later stages, and looked over 
a number that Dr. N. M. Stevens had made in connection with an- 
other study on Ascaris. 
For the spermatogeuesis aud oogenesis, some material was 
sectioued, and stained in thionin or in iron haematoxylin, but it was 
found simpler to stain the tubes whole in alcoholic hydrochloric- 
acid carmine and mount in clove oil, separating the cells partly by 
needles and partly by tapping on the cover glass after mounting. 
This method has the great advantage of enabling one to stud}* the 
cells and chromosomes whole. 
