= 
gd 
Mich has its origin from one of the larger centrosomes. . 
A ttraction-Spheres and Centrosomes. 447 
centrosomes lay. Attraction-spheres and centrosomes vary 
in size in different kinds of cells. Flemming found them 
very small in the epithelial cells of the salamander’s lungs, 
while in leucocytes they were much larger. Biitschli(4) says 
that the centrosomes, observed by him in Surirella, were so 
large that they were visible as a dark round granule even in 
the living cell. 
There was a divergence of opinion, almost from the begin- 
. 
| ting, as to the number of these bodies in each cell. Many 
observers claimed that there was but one in the resting cell, 
and that this one divided before the nucleus began to divide; 
7 while others held that there were two to each resting nucleus, 
md that each of the two divided during nuclear division, so 
that each daughter nucleus was again provided with two. 
Flemming (5), in 1891, found the bodies double much more 
often than single, and he thought that where only one was 
sten the other might be hidden. Heidenhain(15), in 1892, 
tated that the number of centrosomes with each resting nu- 
fus is always two. Guignard (10) also found them always 
double. Birger, van Beneden, and van der Stricht evidently 
hold the opinion that there is only one. Thus there is room 
a doubt as to whether there may not be variation, in some 
ules but one and in some two for each resting cell. 
But Heidenhain (153), in 1894, found in many cases along 
with the two centrosomes a third body, and sometimes a 
| burth, which he regards as an accessory centrosome (Neben- 
“petchen). That is, he thinks that the accessory centro- 
Oe is nothing else than a centrosome of the smallest ee 
giant cells from the bone-marrow of the rabbit he found 
—3€ Numbers of centrosomes grouped together, sometimes 
Smany as 1 35 in a group. There is generally one main 
Pof these bodies in each cell, with one or more smaller 
“eessory groups. : i 
The bodies have been found quite universally in the ae 
ns a8 regards the nucleus. In:the resting cell they 
toy tie in a depression of the nucleus, close together, 
hs during mitosis they are at the poles of the spindle. co 
Mane aon (12), while he holds that the apart: tae ee 
ae organs, believes with O. Hertwig (13) tha z ih 2 
eg lees during its resting stage and only com 
St stages of division. 
