250 
Sidiiey 1. Kornhauser 
were eucountered, usually in two regions: near the attachment of the 
terminal filament and near the base of the chamber or Keindager 
(Plate XVIII, Fig. 10). 
VI. Observations on Spermatogonia and Oögonia. 
A. Enchenopa binotata. 
Spermatogonia of several generations occur at the apex of each 
tnbule and are usually limited to the space bounded by the radiating 
protoplasmic processes of the large apical cell. At the extreme tip of 
the tubule are spermatogonia not enclosed in cyst walls. Often a single 
one is seen dividing (Plate XVIII, Figs. 11, 12), and this division is 
the first in a series of divisions the cells resulting from Avhich belong to 
a single cyst. Small spheroidal cysts of 8, 16, or 32 cells are found dose 
to these primary spermatogonia and below these, interlaced by processes 
of the apical cell, are older cysts. The last spermatogonial division of 
a cyst occurs when the cyst has reached the lower limits of the processes of 
the apical cell; here a large percentage of enthe cysts degeneratc {E. 
binotata-, Plate XVIII, Fig. 8; E. curvata, Plate XVIII, Figs. 11, 12) and 
are utilized, I believe, as nutritive material for the earlier spermatogonial 
generations, the work of assimilating and redistributing this material 
being done by the apical cell. Some of the evidences for this conclusion 
are as foUows: 
First, the substance of the degenerating cysts gradually decreases, 
leaving large spaces between the broken down ceUs; moreover, ruptures 
in the cyst waU are sometimes found in immediate proximity to the 
long processes of the apical ceU, and the degenerating ceUs themselves 
are occasionally found imbedded in the protoplasm of this immense 
nurse cell. When degenerating cysts ai'e present, the cell body and pro- 
cesses of the apical ceU are large and easily traceable; but when no de- 
generating cysts are being absorbed, the processes are smaU. At such 
times the nucleus is ofteii surrounded on one side by a deeply staining 
mass (Plate XVIII, Fig. 13), which may be made up of waste products 
accumulated duriug the period of high metabolic activity and thrown 
out of the nucleus during the period of lower metabolic activity; for the 
nucleus contains very little basic staining material during the period in 
which the cell is accumulating substance. 
Secondly, the critical period in the life of a cyst is immediately after 
the last spermatogonial division, for at no other point in the tubule is 
there evidence of degeneration; it is only in the region of transition from 
