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facts all tend to prove the central corpuscle a mechanical center and there- 
fore an active element in the cell. Whether it is truly homologous with the 
centrosome of actively dividing cells can be determined, it seems to me, 
only by tracing its previous history. If it can be shown that is has remained 
over from the last cell division, then the presence of such a body 
— a true centrosome — in a cell so conservative as a nerve cell 
will be a matter of great theoretical interest. This is a problem in 
ontogenesis which appears to me worthy of strenuous effort, and I 
hope that I may in the end be able to contribute something toward 
the settlement of the question — whether the central corpuscle and 
sphere in nerve cells is genetically connected with the centrosome 
and sphere of dividing cells. 
That such a structure should be present in the nerve cells of 
animals so remotely related as the frog and an annelid, points strongly 
to a far more general occurrence of it in nerve cells; doubtless 
many accounts of its presence in other nerve cells are yet to appear. 
So far, the case would seem to be a strong one for regarding this 
structure as an element, not of the nucleus, but of the cytoplasm. 
In conclusion I would add that the centrosome which I find in 
this annelid agrees more closely with that which DEHLER figures than 
with the one described by v. LENHOSSER. The latter author says 
that in the spinal ganglion cell of the frog the centrosome is made 
up of a large number — more than a dozen — of exceedingly small 
bodies. DEHLER’S figures, on the other hand, show sometimes a single 
corpuscle, sometimes two or three. I have found sometimes one, 
sometimes two or three, in the nerve cells from the annelid which I 
have studied. 
Although v. LENHOSSEK was the first to prove the existence of 
a “centrosome” in a nerve cell, HEIDENHAIN (94, p. 656), it would 
seem, already had a notion that it might be present in such cells, 
for he closes his chapter regarding the universality of the centrosome 
with these words: 
“Kamen wir so zu positiven Resultaten, so würde es der VAN 
BENEDEN - Boverrsschen Theorie von der Ubiquität der Centralkörper 
am Ende nur einen geringen Eintrag thun, wenn sich schließlich 
herausstellen sollte, daß es einige wenige Zellenformen giebt, welche, 
da sie im erwachsenen Tierkörper nicht mehr teilungsfähig sind, die 
Centralkérper völlig einbiiken. Es würde sich, soweit ich das zu 
beurteilen vermag, wohl wesentlich nur um die Ganglienzellen handeln. 
Allein auch hier ist für eine Specialuntersuchung Aussicht auf Erfolg 
