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H. E. Jordan 
cell is retained and that tlie former elongates at right angles to the head. 
Figs. 77 and 78 illustrate spermatozoa at this stage of development in 
side view. Figs. 67 and 78 show the double character of the centrosome. 
From one of these (the distal one apparently) the tail filament grows out. 
One centrosome clearly retains its position at the head of the filament 
as an end-knob but the fate of the other is uncertain. It probably wanders 
to the distal end of the middle piece, forming its non-mitochondrial portion 
— or possibly its sheath — but among the numerous mitochondria crowd- 
ing this region it cannot be definitely identified. 
Figs. 76 to 79 show later stages in the development of the head and 
body of the Spermatozoon. The head (i. e. compact nucleus) is split, now 
having a U-shape, apparently solid toward the bend (fig. 76). Mitochondria 
are abundantly present in the body. The split in the head seems due to 
an in-pushing and down-pushing of the Nebenkern. Here it remains 
for a time (figs. 81, 83 and 85) but ultimately seems to disappear leaving 
a V-shaped space in the anterior ventral portion of the head and body, 
its upper margin formed laterally by the the limits of the U-shaped head 
and dorsally by the mass of cytoplasm bearing the middle piece. The 
main portion of the Nebenkern envelops the head (figs. 77 and 78) and 
delimits that portion of the cytoplasm which is to form the “body”. The 
form of the head and body of the Spermatozoon at this stage, and sub- 
sequently, consequently resembles somewhat a funnel (or lily) with a 
V-shaped space in the anterior ventral portion. It remains to state simply 
that mitochondria (chondriosomes) wander inward and take a position 
about the axial filament to form the spiral filament of the middle-piece 
(figs. 78 to 86). The middle-piece seems enclosed by a membrane and the 
whole is contained in a thick mass of protoplasm which thins out ventrally 
and is continuous to the V-shaped interruption. The cephalic portion 
of the Spermatozoon thus consists of a funnel-shaped structure, the margins 
of which are formed by the U-shaped head (nucleus open in front) and the 
dorsal wall of wliich (cytoplasmic) is thickened to contain the middle- 
piece. The constricted tubulär portion of the “funnel” is represented by 
a very long tail consisting of cytoplasm and axial filament. Nowhere in 
my material have I seen the paired spermatozoa described by Selenka 
(1887) for the vas deferens of the oppossum. The conjugation of the 
spermatozoa woiüd consequently seem to be a secondary matter. Ballo- 
witz (1895) described such secondary conjugation of the primarily se- 
parate Spermatozoon also in beetles (Dytiscidae) where even three or 
more may unite to form an independent “spermatozeugma” 4 ). 
