THE BIOLOGY OF ASCIDIANS
31
a
1
FIO. 14. Sycozon aigillinoidee. Colonies. a, with stalk and fully developed heads; b, with
hoadlcss stalks; c, with new heads developing from an old stalk.
portant since the parent zooids nourish the embryos for several
months .
Colonies not only may divide, but in some species may fuse.
Bancroft (1903) found in Botryllus sp. and Botrylloides sp. that unrelated colonies would not fuse, but that closely related colonies might
do so. Further investigations by Oka and Watanabe (1957, 1960) and
by Mukai (1967) revealed something of the genetic basis of the phenomenon but the extent to which fusion occurs in nature remains uncertain.
The life-span, like the growth-rate, is more difficult to determine in
compound than in simple ascidians, because of their periodic reduction
and regeneration. There may even be grounds for regarding the colony
of some species as potentially immortal (Sabbadin, 1960). In the field
it is difficult to identify and follow the fate of individual colonies, and
31
a
1
FIO. 14. Sycozon aigillinoidee. Colonies. a, with stalk and fully developed heads; b, with
hoadlcss stalks; c, with new heads developing from an old stalk.
portant since the parent zooids nourish the embryos for several
months .
Colonies not only may divide, but in some species may fuse.
Bancroft (1903) found in Botryllus sp. and Botrylloides sp. that unrelated colonies would not fuse, but that closely related colonies might
do so. Further investigations by Oka and Watanabe (1957, 1960) and
by Mukai (1967) revealed something of the genetic basis of the phenomenon but the extent to which fusion occurs in nature remains uncertain.
The life-span, like the growth-rate, is more difficult to determine in
compound than in simple ascidians, because of their periodic reduction
and regeneration. There may even be grounds for regarding the colony
of some species as potentially immortal (Sabbadin, 1960). In the field
it is difficult to identify and follow the fate of individual colonies, and