160
R. K. DELL
known in some other members of the family such as Myochuma and
Cochlodesma but was not known to Burne in any other species of
Laternula. In the Montacutidae, Montacuta bidentata (Montagu) and
M . ferruginea (Montagu) incubate the eggs for some time but veligers
are released so that there is a restricted pelagic larval life (Thorson,
1946). Cyamiocardium dahli Soot-Ryen from Chile is another species in
this genus which incubates the eggs (Soot-Ryen, 1951, p. 46). Probably
many additional species in the Antarctic will prove to have a similar
habit when more is known of their biology. In order to interpret this
phenomenon properly, much more will need to be known of the reproductive habits of non-Antarctic members of these families.
It may be noted that all the species listed above except for Mysella
arthuri and Cyamiocardium crassilabrum have achieved wide dispersal
so that the incubatory habit in itself is no barrier to possible dispersal
and may be a distinct advantage as regards establishment of a species
in a new area.
C. Ascidiacea
Kott (1969a) discussed the incidence of viviparity amongst Antarctic
ascidians. The families Styelidae, Molgulidae and Agnesiidae, and the
subfamily Polyzoinae, amongst which there are many viviparous species
in general, are well represented in the Antarctic. The members of the
suborder Aplousobranchia are generally viviparous, but some Antarctic species such as Synoicium adareanum (Herdman) and s. georgianum (Sluiter) retain the larvae until they metamorphose within the
adult test. Species of the suborders Phlebobranchia and Stolidobranchia,
members of which are not usually viviparous, have also acquired this
habit in Antarctic waters.
D. Polychaeta
Gravier (1911d) discussed some examples of incubation of eggs in
polychaetes collected by the Second French Antarctic Expedition. In
Eteone gaini Gravier, the eggs form a compact mass tightly enclosed
between the lateral and ventral aspects of the worm, where they are
enclosed by a membrane secreted by the animal. In Flabelligera
rnundata Gravier, the anterior part of the body is enclosed by curved,
long bristles which form a kind of cage. Inside this, between the palps
and gills, the eggs are deposited in groups.
Hartman (1967~) described the peculiar breeding habit of the tube
dwelling Nothria notialis (Monro). Some of the tubes collected contained
lateral capsules, with a single adult in the main tube and juveniles at
various stages of development in the lateral capsules. This is in contrast
R. K. DELL
known in some other members of the family such as Myochuma and
Cochlodesma but was not known to Burne in any other species of
Laternula. In the Montacutidae, Montacuta bidentata (Montagu) and
M . ferruginea (Montagu) incubate the eggs for some time but veligers
are released so that there is a restricted pelagic larval life (Thorson,
1946). Cyamiocardium dahli Soot-Ryen from Chile is another species in
this genus which incubates the eggs (Soot-Ryen, 1951, p. 46). Probably
many additional species in the Antarctic will prove to have a similar
habit when more is known of their biology. In order to interpret this
phenomenon properly, much more will need to be known of the reproductive habits of non-Antarctic members of these families.
It may be noted that all the species listed above except for Mysella
arthuri and Cyamiocardium crassilabrum have achieved wide dispersal
so that the incubatory habit in itself is no barrier to possible dispersal
and may be a distinct advantage as regards establishment of a species
in a new area.
C. Ascidiacea
Kott (1969a) discussed the incidence of viviparity amongst Antarctic
ascidians. The families Styelidae, Molgulidae and Agnesiidae, and the
subfamily Polyzoinae, amongst which there are many viviparous species
in general, are well represented in the Antarctic. The members of the
suborder Aplousobranchia are generally viviparous, but some Antarctic species such as Synoicium adareanum (Herdman) and s. georgianum (Sluiter) retain the larvae until they metamorphose within the
adult test. Species of the suborders Phlebobranchia and Stolidobranchia,
members of which are not usually viviparous, have also acquired this
habit in Antarctic waters.
D. Polychaeta
Gravier (1911d) discussed some examples of incubation of eggs in
polychaetes collected by the Second French Antarctic Expedition. In
Eteone gaini Gravier, the eggs form a compact mass tightly enclosed
between the lateral and ventral aspects of the worm, where they are
enclosed by a membrane secreted by the animal. In Flabelligera
rnundata Gravier, the anterior part of the body is enclosed by curved,
long bristles which form a kind of cage. Inside this, between the palps
and gills, the eggs are deposited in groups.
Hartman (1967~) described the peculiar breeding habit of the tube
dwelling Nothria notialis (Monro). Some of the tubes collected contained
lateral capsules, with a single adult in the main tube and juveniles at
various stages of development in the lateral capsules. This is in contrast