306
P. 9. MEADOWS AND J. I. CAMPBELL
species where the larvae of one, S. spinulosa, always prefers the sand
tubes of its own species to those of S. alveolata, but where larvae of the
other, S. alveolata, show the same preference, that is, prefer S. spinulosa
tubes to those of their own species as long as the tubes have been
constructed in the laboratory (Wilson, 1970a, p. 28-30). In a letter to
the authors, Wilson (1972) states “ I think it would be as well to point
out that the preference shown by alveolata larvae for spinulosa tubes is
only for tubes built in laboratory tanks. When natural spinulosa tubes
from the sea are offered with natural alveolata tubes, both together in
the same dish, the former are nothing like as attractive to the larvae
as are the latter, though the former w i l l induce metamorphosis when
TABLE III. SPECIES RECOGNITION DURINQ GREGARIOUS SETTLEMENT.
Larvae of Spirorbis borealis and Spirorbis pagenstecheri were put together into a
dish containing a number of slate panels. Each slate either bore previously
settled S. borealis or previously settled S. pagensteoheri (Knight-Jones, 1951,
Table 5. Summary of experiments 1-10).
No. of
No. of
Choke
hmae
larvae
settling
settling
on slatea
on slates
S. borealis
8. pagenstecheri
Slates bearing previously
settled S. borealis
217
97
Slates bearing previously
settled S. pagemtecheri
86
204
present alone.” Neither Wilson nor we can account for these laboratory
findings. Since no colonies are recorded containing the two species
together in the field, one must suppose that other as yet unrecognized
aspects of the behaviour of S. alveolata larvae prevent them from joining
S. spinulosa colonies or that the laboratory tubes of spinulosa are
peculiar in some way.
The species specific response of larvae to intact adults are
paralleled by specificity at a chemical level. Metamorphosis of the
larvae of the ascidian Phallusia nigra Savigny is rapidly and consistently induced by extracts of adult P. nigra but not by extracts of
adult Polyandrocarpa tincta, and thereverse is true of the metamorphosis
of P. tincta larvae (Grave, 1936). The cypris larvae of Balanus balanoides and of Elminius modestus distinguish clearly between extracts
of their own adults and extracts of adults of the other species in
P. 9. MEADOWS AND J. I. CAMPBELL
species where the larvae of one, S. spinulosa, always prefers the sand
tubes of its own species to those of S. alveolata, but where larvae of the
other, S. alveolata, show the same preference, that is, prefer S. spinulosa
tubes to those of their own species as long as the tubes have been
constructed in the laboratory (Wilson, 1970a, p. 28-30). In a letter to
the authors, Wilson (1972) states “ I think it would be as well to point
out that the preference shown by alveolata larvae for spinulosa tubes is
only for tubes built in laboratory tanks. When natural spinulosa tubes
from the sea are offered with natural alveolata tubes, both together in
the same dish, the former are nothing like as attractive to the larvae
as are the latter, though the former w i l l induce metamorphosis when
TABLE III. SPECIES RECOGNITION DURINQ GREGARIOUS SETTLEMENT.
Larvae of Spirorbis borealis and Spirorbis pagenstecheri were put together into a
dish containing a number of slate panels. Each slate either bore previously
settled S. borealis or previously settled S. pagensteoheri (Knight-Jones, 1951,
Table 5. Summary of experiments 1-10).
No. of
No. of
Choke
hmae
larvae
settling
settling
on slatea
on slates
S. borealis
8. pagenstecheri
Slates bearing previously
settled S. borealis
217
97
Slates bearing previously
settled S. pagemtecheri
86
204
present alone.” Neither Wilson nor we can account for these laboratory
findings. Since no colonies are recorded containing the two species
together in the field, one must suppose that other as yet unrecognized
aspects of the behaviour of S. alveolata larvae prevent them from joining
S. spinulosa colonies or that the laboratory tubes of spinulosa are
peculiar in some way.
The species specific response of larvae to intact adults are
paralleled by specificity at a chemical level. Metamorphosis of the
larvae of the ascidian Phallusia nigra Savigny is rapidly and consistently induced by extracts of adult P. nigra but not by extracts of
adult Polyandrocarpa tincta, and thereverse is true of the metamorphosis
of P. tincta larvae (Grave, 1936). The cypris larvae of Balanus balanoides and of Elminius modestus distinguish clearly between extracts
of their own adults and extracts of adults of the other species in