WILCOX: SPERMATOGENESIS OF CALOPTENUS FEMUR-RUBRUM. 199 
I have not seen these structures in the spermatogonia and spermato- 
cytes of Caloptenus, and my failure to see them can hardly have been 
due to the use of methods not suited to the differentiation of such 
structures ; for the interzonal filaments are clearly shown in Figures 
31-35 and 39-44. Very similar conditions are seen in the first division 
of the spermatocytes, but I have not been able to discover that the 
remnants of the spindle persist from one cell generation to another. 
The spindle remains do persist, however, after the second division of the 
spermatocytes, and as I have shown, go to form in the spermatid of 
Caloptenus the body which I have called the “ Nebenkern," just as 
Field (93) has shown for Echinoderms. 
I cannot keep entirely free from the present active controversy as to 
the existence, origin, and meaning of the centrosomes. So far as my 
own observations on spermatogenetie material go, there certainly are 
distinet sharply contoured bodies at the point toward which the fibres 
converge at either end of the spindle. Each body is single, and I can- 
not resolve it, even with a magnification of 1,500 diameters. I have 
represented in Plate 1, Figs. 1 and 2, centrosomes during the division 
of the spermatogonia ; in Plate 1, Figs. 19-25, during the first division 
of the spermatocytes; in Plate 2, Figs. 31, 38, Plate 3, Fig. 111, during 
the second spermatocyte division; and in Plate 3, Figs. 77-110, during 
the metamorphosis of the spermatids. Between the last division of the 
spermatogonia and the first spermatocyte division, I am unable to say 
what becomes of the centrosomes. From the first maturation division 
to the formation of the spermatozoön, the centrosome maintains, as I be- 
liove, its individuality, and undergoes only slight changes. My material 
was not favorable for following the early history and origin of the cen- 
trosomes, and I therefore cannot from personal experience criticise the 
following account by Reinke (94, p. 276): “Ich halte demnach die 
Centralkórper nicht für Gebilde sui generis, wie etwa den Kern, ‘und 
möchte sie auch nicht für em Organ der Zelle, das an einer bestimmten 
Stelle liegen müsste, erklären, sondern ich halte sie für organoide Gebilde, 
die sich nach Bedürfniss aus kleineren ähnlichen, im Protoplasma über- 
all vorhandenen Gebilden (tertiüren Centren) entwickeln können, also 
potentiell in der Marksubstanz der Zelle überall vorhanden sind,” ete. 
Reinke thus considers centrosomes as organoids, not organs of the 
cell. This may be the true origin of the centrosomes, but I firmly be- 
lieve that in Caloptenus they are not broken up into microsomes after 
the first division of the spermatocytes. 
