96
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
of these, A . ephippium, is a synonym for A . simplex. Other references can be found in the above-mentioned articles of Jrargensen and
Sullivan.
Large A . simplex can be conditioned in Deoember and induced to
spawn during the first part of January. Some conditioned groups were
induced to spawn several times between the middle of January and the
beginning of August. To induce spawning presented no problem
because, usually, ripe animals began to spawn as soon aa the temperature of the water was raised only a few degrees above 20°C. Even
in summer it was not necessary to raise the temperature much above
25°C. I n many instances spawning began without addition of any sex
products, a circumstance which is unusual in our experiences with
spawning of other bivalves.
Artificial fertilization of A . simplex eggs is possible. Stripping can
be easily accomplished by gently washing the light yellow gonad
tissue of a female in sea water. The eggs separate easily and many
remain uninjured. Therefore, a high percentage of them ordinarily
develop into normal larvae.
Compared with eggs of other bivalves, eggs of A . simplex are comparatively small, ranging only from 42 to 45 p in diameter. Because
of their small size the eggs are difficult to handle, as they easily pase
through the mesh of the smallest screen used for egg retention. Becauee
eggs and early larvae cannot be strained and, thus, separated from the
surrounding water, as is done with larger eggs, in fertilizing eggs of
A . simplex care should be taken not to use too much sperm so as not
to pollute later cultures of developing eggs and early larvae.
In our cultures of A . simplex the smallest larva with completely
formed shells measured approximately 58 x 47 p. Young larvae are
more fragile and transparent than those of C. virginica of corresponding
stages. The " straight-hinge " is actually sloped about 5" so that it is
somewhat convex. This is difficult to observe under a microscope unless
larvae are seen precisely in profile.
The most common size at which larvae of A . simplex metamorphosed was at a length of 195 to 210 p. The largest swimming larva8
measured approximately 215 x 220 p. We cannot compare the dimensions and shapes of our larvae with those given by Stafford (1912)
because his drawings and measurements bear little resemblance to the
larvae of A . simplex in our cultures.
Sullivan ( 1948) gave the smallest size of A . acuEeata aa 1 10 x 100 p,
and the largest as 285 x 280 p. Jrargensen (1946), in referring to his
own observations on A . sqwzmuh, reported that the smallest larvae
measured 65 to 75 p in length, and the largest attained a length of
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
of these, A . ephippium, is a synonym for A . simplex. Other references can be found in the above-mentioned articles of Jrargensen and
Sullivan.
Large A . simplex can be conditioned in Deoember and induced to
spawn during the first part of January. Some conditioned groups were
induced to spawn several times between the middle of January and the
beginning of August. To induce spawning presented no problem
because, usually, ripe animals began to spawn as soon aa the temperature of the water was raised only a few degrees above 20°C. Even
in summer it was not necessary to raise the temperature much above
25°C. I n many instances spawning began without addition of any sex
products, a circumstance which is unusual in our experiences with
spawning of other bivalves.
Artificial fertilization of A . simplex eggs is possible. Stripping can
be easily accomplished by gently washing the light yellow gonad
tissue of a female in sea water. The eggs separate easily and many
remain uninjured. Therefore, a high percentage of them ordinarily
develop into normal larvae.
Compared with eggs of other bivalves, eggs of A . simplex are comparatively small, ranging only from 42 to 45 p in diameter. Because
of their small size the eggs are difficult to handle, as they easily pase
through the mesh of the smallest screen used for egg retention. Becauee
eggs and early larvae cannot be strained and, thus, separated from the
surrounding water, as is done with larger eggs, in fertilizing eggs of
A . simplex care should be taken not to use too much sperm so as not
to pollute later cultures of developing eggs and early larvae.
In our cultures of A . simplex the smallest larva with completely
formed shells measured approximately 58 x 47 p. Young larvae are
more fragile and transparent than those of C. virginica of corresponding
stages. The " straight-hinge " is actually sloped about 5" so that it is
somewhat convex. This is difficult to observe under a microscope unless
larvae are seen precisely in profile.
The most common size at which larvae of A . simplex metamorphosed was at a length of 195 to 210 p. The largest swimming larva8
measured approximately 215 x 220 p. We cannot compare the dimensions and shapes of our larvae with those given by Stafford (1912)
because his drawings and measurements bear little resemblance to the
larvae of A . simplex in our cultures.
Sullivan ( 1948) gave the smallest size of A . acuEeata aa 1 10 x 100 p,
and the largest as 285 x 280 p. Jrargensen (1946), in referring to his
own observations on A . sqwzmuh, reported that the smallest larvae
measured 65 to 75 p in length, and the largest attained a length of