80 GERM-CELL CYCLE IN ANIMALS 
tive ability of these animals and must also account 
for the development of plasmodia formed by dis- 
sociated cells (Wilson, 1911; Miiller, 1911) into 
adult sponges with all specific characteristics in- 
cluding reproductive bodies. 
It therefore seems possible that there may exist 
in the sponges a continuity of the germ-plasm and 
that the germ-cell material is distributed among 
thousands of cells (tokocytes, see Table, p. 71) 
which are derived from archeocytes, and that under 
proper conditions these tokocytes may produce 
odgonia or spermatogonia, or may aggregate to 
form gemmules or regenerative bodies. This wide 
distribution of the germ cells is what might be 
expected in such lowly organized animals. Figure 
28 shows the probable history of the germ cells in 
the Portrera from one generation to the next. 
2, CG@LENTERATA 
The origin of the germ cells in the C@LENTERATA 
has been a much debated subject among zodélogists 
for three-quarters of a century. As early as 1843 van 
Beneden undertook to determine the germ layer 
from which the germ cells arise and concluded that 
the ova originate in the entoderm and that the 
spermatozoa come from the ectoderm. F. E. 
Schulze (1871) claims that in Cordylophora both 
the ova and spermatozoa are of ectodermal origin. 
Kleinenberg (1872), working on Hydra, announced 
that the germ cells are interstitial in origin and, 
since the interstitial cells arise from the ectoderm, 
