312 
D? L. SOÓS 
coalesce, and thus originate ringlike structures (PL VIII., Fig. 6.). But 
it would be an error to conclude the true structure from the appearence 
of the figures as it was done by Bolles Lee. It is not to be forgotten 
that we see in such cases, as a rule, the optical sections of the chromo¬ 
somes, the form of which varies naturally according to the direction of 
the cut ; nor less important is the fact that we have not yet definite, 
but developing chromosomes before us. Their careful study shows they 
consist at this stage of a quite irregular groups of chromomeres. 
We can regard the chromosomes as definitely formed when their 
chromomeres melt together into a homogeneous mass, and their outlines 
become smooth and sharp. Their shape is even then irregular, spherical 
or polymorphic. They lie, as a rule, immediately under the nuclear 
membrane, to which they are very often attached (PL VIII., Fig. 9.). 
The number of the chromosomes is in this stage well countable, and 
we can determine that they are present in reduced numbers. The greatest 
number which I could accurately count was 21 ; the true number with 
the greatest probability is that found by the authors (Platner, Bolles Lee, 
Ancel) in the spermatocytes of Helix pomatia, i. e. 24. 
The chromosomes of Enteroxenos Östergreni, according to the 
researches of Bonnevie (13, 14), develope in quite the same manner as 
those of H. arbustorum, but the nuclear membrane in Enteroxenos 
dissolves earlier, i. e. then, when the chromosomes are represented by 
irregular loose groups of chromomeres. 
Synchronously with the definite forming of the chromosomes appears 
also the centrosome which is to be found then in the cytoplasm close 
to the nuclear membrane (PL VIII., Figs. 7., 8.). The centrosome of 
H. pomatia, according to Bolles Lee (10), first appears within the 
pucleus, and its presence can be determined before the definite forma¬ 
tion of the chromosomes. It passes out of the nucleus only at the end 
of the prophase. Similar observation has been made by Brauer (17) in 
Ascaris megalocephala. I have not found any sign of its appearing 
within the nucleus though I worked also with Bolles Lee’s methods. 
I was able to determine its presence with certainty when it was already 
lying in the cytoplasm, and was surrounded by astral rays. The centro¬ 
some is at that time very small, and consists only of the centri ole, the 
centrosphere appearing later. The centriole soon dividesor perhaps 
it was even earlier double like in Ascaris according to 0. Hertwig (48) — 
and the two corpuscles pass along the nuclear membrane toward the 
opposite poles of the cell (PL VIII., Fig. 8.). 
The nuclear membrane at the beginning of the metaphase disap¬ 
pears (PL IX., Fig. 5.), and the centrioles which have then also centro- 
