682 MURIEL ROBERTSON. 
be in brief as follows :—The Trypanosome ingested with the 
blood develops in a few hours into a flagellate, rather rounded 
and broad in shape. It may grow very considerably in size, 
and adopt the T'rypanosome condition, i.e. with the kineto- 
nucleus posterior to the trophonucleus. Division still proceeds. 
Great variation in shape and size occurs in this middle period 
of digestion, and the relative position of the two nuclei varies 
very much even in the two products of one division. All 
stages from the round, rather dumpy crithidia to immensely 
long and very slender forms moving with great rapidity 
darting across the field in a flash are to be seen in the crop 
at the same time. 
These different forms will be described in greater detail 
when the stained material comes to be considered. Division 
stages may also be seen, and these are often unequal. 
Towards the end of digestion the type becomes much more 
uniform, and slender forms with little protoplasm and flagella 
hardly exceeding the length of the body seem to dominate to 
the exclusion almost entirely of other forms. These creatures 
very often have the kinetonucleus just anterior to and almost 
embedded in the trophonucleus. They seem at this stage, 
moreover, to have reached the hmit of division as dividing 
figures were never found. It appears probable that death 
would now ultimately supervene unless injected into the 
blood of the vertebrate host. 
Conjugation was carefully watched for, but no sign of it 
was found. It was expected to occur probably immediately 
after the first divisions in the leech or else possibly towards 
the close of the middle period of digestion. 
The process of conjugation might of course occur at another 
point of the life-cycle, namely, at the time when the 'Trypano- 
some is injected from the alimentary tract of the leech into 
the circulation of the tortoise. If that were the case it would 
amply explain the elusive character of this process amongst 
Trypanosomes, as that is the one part in the cycle of a plasma 
dwelling form which it is almost impossible to investigate 
properly. 
