302 M. M. Mercaur 
soon to be published by v. Prowazex, leaves no doubt of the 
existence of reduction in Trypanosomes. Several as yet unpublished 
papers by Harrmann and his students show reduction division in 
Amoeba and Flagellata. In Opalina we find clearly a reduced number 
of chromosomes in the gametes, and it is easy to see that the usual 
full number is restored by copulation. I have not found how the 
reduction is effected, but that it occurs is beyond doubt. 
It is interesting to note that the diminished number of chromosomes 
appears long before copulation, in animals from four to eight times 
too large for encystment. Four chromosomes are found in the nuclei 
for at least four generations before copulation, and probably for a still 
longer period. It is impossible to say how many times the animals 
divide after leaving the cysts before they are ready for copulation. 
It is possible that for a time the appearance of fewer chromosomes 
is due to their bivalence.’) If the smaller number is due from the 
first to true reduction division, and apparently this is true, we have 
the interesting fact that the condition with a reduced number of 
chromosomes persists for several generations. In Metazoa fertilization, 
immediately follows the maturation divisions. 
NERESHEIMER (1907) has compared the extrusion of the two 
chromatin spheres in Opalina to the formation of the two polar bodies 
in Metazoa, a comparison which seems wholly unjustified.2) The 
chromatin spheres neither of them consist of whole chromosomes, 
but, like the chromatin spherules, are formed from chromatin given 
off from all the chromosomes. In some nuclei in which the chromatin 
spheres are present one sees eight chromosomes remaining in the 
nucleus, in other cases four chromosomes are found, showing that the 
formation of these spheres may occur before the number, of chromo- 
somes is diminished and that it is a process distinct from that by 
which the diminished number of chromosomes is brought about. As 
a further objection to NerESHEIMER’s interpretation of the chromatin 
spheres, which he seems to have based only upon their number and 
1) In the preliminary notice of this work (Metcatr 1907a) I wrote “These 
chromosomes [of reduced number], as seen in the living animals, show about half 
as many granules as do the chromosomes of the full grown individuals”. Further 
study of carefully stained material in all stages of the spring phenomena is 
necessary before further treatment of this interesting point will be profitable. 
*) NerESHEIMER had already described a series of phenomena which would 
necessitate the nuclei at this stage being interpreted as purely generative nuclei 
formed from generative chromidia, which prevented his interpreting the chromatin 
spheres as vegetative chromidia. 
