7. THE PHYLA NEMERTINEA, ASCHELMINTHES AND ANNELIDA
273
1948; Stauber, 1947, 1950a; Loosanoff and Nomejko, 1951 ; Hillman,
1964 ; and others), even along a relatively similar zoogeographical
range such as the Atlantic coast of North America. Since strains,
varieties, genetic races, or physiological species, terms commonly
employed to designate morphologically similar but functionally
different organisms (see Bates, 1940), are generally accepted as possible
manifestations of speciation, and since geographic isolation is recognized as an important factor in the origin of new species, it would not
be a t all surprising, I think, to find that the Hawaiian “ variety ” of
C . virginica is physiologically distinct from the New England “ variety ”.
Thus, it is possible that if the incompatibility of Hawaiian C . virginica
is real, it may be due to strain differences. Indeed, differences in
susceptibility to zooparasites in C. virginica, for example to Minchinia
nelsoni, is well known. Relative to this point, Stauber’s (1950) statement pertaining to observed differences among strains of marine
molluscs should be heeded with great attention. He has stated :
The presence of such physiological species, each the result of selection over
long periods of time in situations almost completely isolated from each
other and with quite different hydrographical conditions, might explain, for
example, some of the other differences already reported between oysters
from different areas. Caution is suggested in generalization on the basis of
observations on a single variety under study until the nature of these
temperature (and other) variants is adequately disclosed.
111. Phylum ANNELIDA
Several species of polychaetous annelids are known to live in association with marine molluscs (see Clark, 1956). Among these, some have
been found associated with molluscs of commercial importance.
Relative to the nature of the relationship between these annelids and
their hosts, Clark has pointed out :
Although some worms are almost always, or even exclusively, to be found
in more or less intimate association with other animals, very little structural
adaptation appears to have taken place to suit them to this mode of life.
Whether or not physiological adaptations have been evolved remains unknown for the most part.
Loosanoff and Engle (1943) are more definite in their statement. They
are of the opinion that at least the members of the genus Polydora are
definitely not parasites. Until more precise information becomes
available, these annelids are only briefly mentioned herein.
The best known of the polychaetes associated with marine molluscs
of commercial importance are the so-called mudworms of the genus
A.l-1.B.-5
18
273
1948; Stauber, 1947, 1950a; Loosanoff and Nomejko, 1951 ; Hillman,
1964 ; and others), even along a relatively similar zoogeographical
range such as the Atlantic coast of North America. Since strains,
varieties, genetic races, or physiological species, terms commonly
employed to designate morphologically similar but functionally
different organisms (see Bates, 1940), are generally accepted as possible
manifestations of speciation, and since geographic isolation is recognized as an important factor in the origin of new species, it would not
be a t all surprising, I think, to find that the Hawaiian “ variety ” of
C . virginica is physiologically distinct from the New England “ variety ”.
Thus, it is possible that if the incompatibility of Hawaiian C . virginica
is real, it may be due to strain differences. Indeed, differences in
susceptibility to zooparasites in C. virginica, for example to Minchinia
nelsoni, is well known. Relative to this point, Stauber’s (1950) statement pertaining to observed differences among strains of marine
molluscs should be heeded with great attention. He has stated :
The presence of such physiological species, each the result of selection over
long periods of time in situations almost completely isolated from each
other and with quite different hydrographical conditions, might explain, for
example, some of the other differences already reported between oysters
from different areas. Caution is suggested in generalization on the basis of
observations on a single variety under study until the nature of these
temperature (and other) variants is adequately disclosed.
111. Phylum ANNELIDA
Several species of polychaetous annelids are known to live in association with marine molluscs (see Clark, 1956). Among these, some have
been found associated with molluscs of commercial importance.
Relative to the nature of the relationship between these annelids and
their hosts, Clark has pointed out :
Although some worms are almost always, or even exclusively, to be found
in more or less intimate association with other animals, very little structural
adaptation appears to have taken place to suit them to this mode of life.
Whether or not physiological adaptations have been evolved remains unknown for the most part.
Loosanoff and Engle (1943) are more definite in their statement. They
are of the opinion that at least the members of the genus Polydora are
definitely not parasites. Until more precise information becomes
available, these annelids are only briefly mentioned herein.
The best known of the polychaetes associated with marine molluscs
of commercial importance are the so-called mudworms of the genus
A.l-1.B.-5
18