92 
Fic. 30.— Diagram to illustrate the migra- 
tion of the germ cells in hydromeduse 
from their remotely shunted place of origin 
to their primitive place of origin in the 
gonophore, in which they attain to ma- 
turity. The state of affairs in Eudendrium 
is taken as the basis of the diagram. mu, 
mouth; ma, gut-cavity; ¢t, tentacle; Sta, 
stem; A, a branch of the polyp-colony; 
SP, lateral polyp; Gph, a medusoid-bud 
completely degenerated into a mere gono- 
phore; Ei, ovum; GH, gastric cavity; 
st, supporting lamella. The originative 
area of the germ cells lies in the stem of 
the principal polyp at kz’’”’, whence the 
germ cells first migrate into the endo- 
derm of the branch (A) at kz’’’, creeping 
within which they reach kz” in the lat- 
eral polyp (blastostyle), finally reaching 
the gonophore (kz) and passing again 
into the ectoderm. (After Weismann, 
1904.) 
GERM-CELL CYCLE IN ANIMALS 
Podocoryne. Al- 
though perfect 
medusoids are 
formed, these 
have their germ- 
cells fully devel- 
oped at the time 
of their liberation 
from the hydroid 
colony. But in 
species in which 
the medusoid- 
buds have really 
degenerated and 
are no longer lib- 
erated, the birth- 
place of the germ- 
cells is shifted 
even farther back, 
and in the first 
place into the 
stalk (St, kz’’) of 
the polyp from 
the gonophore- 
buds. This is the 
case in the genus 
Hydractinia. In 
the further course 
of the process the 
birthplace of the 
germ-cells has 
