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Alice M. Boring 
case which I have fouud, agrees in every particular with these last 
mentioued and tlierefore the small chromosome fonnd here, must 
liave a maternal origin i). 
In spite of the fact that some worms are without a small chro- 
mosome, and sorae have it in a very small percent of the eggs, still 
when it is present, it has a definite chromosome character, it stains 
like the other chromosomes, and divides when they do. Figure 10 
shows it in metaphase and Figures 11a and 11b are the two anaphase 
plates from one first cleavage spindle. It does not degenerate or 
disappear immediately after the first cleavage division, as it occurs 
in the cells of the germ track, up to the last division to form the 
two primary germ cells (Fig. 13). What becomes of it in the somatic 
cells after diminution is an interesting question that is difficult to 
solve as it is usually about the length of the euds that are thrown 
oÖ' and degenerate in a diminution division, and therefore in such a 
division, it would not usually he possible to recoginze it. Boveri 
has found that the ends of the cliromosftmes at diminution can he 
much more clearly seen in univalens than in hivalens^ and it is 
often possible to count the four, two from each of the two chromo- 
somes. If the small chromosome is not a fragment, but a distinet 
unit in itself, it might be possible to find it in univalens in a dimi- 
mition division, as then there sliould he five such pieces present, 
instead of the usual four. 
The uext question of interest is whether this small chromosome 
appears in the eutire cycle of development. It may be present as 
we have seen, from the first cleavage to the primary germ cells and 
is proved in many cases to come from the Spermatozoon and in one 
case possibly from the egg also. Is it i)reseut in oogonia and sper- 
matogonia and in the maturation divisious? tspermatogonial equa- 
torial plates were studied in thirteen males taken from the some four 
horses as four of the females used for eggs. Many preparations were 
made and the small chromosome fouud only three times, twice in an 
aceto-carmiue preparation of the testis of a very young male 
(Fig. 14) and ouce in another worin. The spermatocyte divisious in 
some of these thirteen worms were studied, and no trace of the 
small chromosome was found. It appeared at first so likely that the 
q An interesting case was found of an egg with three Chromosomes and 
with tliree rods in tlie second polar body, suggesting that one entire dyad in 
the second maturation division had passed undivided into the second polar 
body, wliile the other had divided normally (Fig. 9). 
