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BULLETIN OF THE BUREAU OF FISHERIES 
Numerous similar attempts were made (a close following of Belding’s method 
having uniformly failed), generally with poor or no success. If eggs were obtained 
sperms would not be obtained or would not fertilize the eggs. 
Once some success was obtained accidentally. A scallop out of water, being 
measured, squirted out about a quarter of a teaspoon of pink eggs. This scallop 
was placed in a bowl of sea water where it continued to emit vast numbers of eggs. 
Three other scallops were placed in separate bowls. These cast sperms. Water in 
which the sperms were most active was poured into that containing eggs. Larvae 
from this lot lived to be 3 days old. 
Although scallops sometimes, particularly late in the season, discharge a large 
portion of their sexual products in a brief time, from observations of the gonads it 
appears that in North Carolina individuals ordinarily spawn over a considerable 
period. This is in accord with the observations of Belding (1910). 
FERTILIZATION AND EMBRYONIC DEVELOPMENT 
Fertilization normally is external and consists in the union of the small, active 
sperm with the egg. Testicular sperms which appear mature are about 0.05 milli- 
meter long, with heads 0.001 to 0.0012 millimeter long. These dimensions are con- 
siderably different from those shown by Belding (1910) for cast sperms (length about 
0.07 millimeter, head about 0.0006). Ovarian eggs may be about 0.063 by 0.06 
millimeter (sample measurement), but with shape varying. These measurements 
correspond well with Belding’s scale drawings of cast eggs. The sperms swim until 
they come in contact with an egg (or perish), about one of which great numbers may 
cluster with heads toward the egg. Normally only one enters (see Belding, 1910), 
fertilization occurs, and development begins. 
Scallop embryology has been studied by Fullarton (1890), Drew (1906), and 
Belding (loc. cit.) and is included in the general statement of Korschelt (1900). Em- 
bryonic development is of the typical lamellibranch type with unequal cleavage and 
without blastula. (See fig. 21 .) A yolk lobe which resembles a micromere, appearing 
before the second micromere and later absorbed by the macromere, is described and 
figured by Belding and Drew. The gastrula is epibolic. At this stage the embryo 
is well supplied with cilia and rolls about in the water. Belding obtained this stage 
in about 10 hours. Next a trochophore is formed. Belding obtained this stage in 
12 to 14 hours, but the writer not so quickly (from about 1 to nearly 2 days at about 
25° C.). This takes the scallop through the embryonic into the larval stage. 
LARVAL DEVELOPMENT 
The earliest larva (fig. 21), termed the trochophore (or trochosphere) from its 
resemblance to the annelid larva of the same name, possesses besides shorter cilia, 
a flagellum which appears to be single but has been found (Belding, 1910) to be a 
close tuft of as many as six large cilia. A primitive digestive tract is present. At 
this stage the animal swims forward (flagellum in advance) and rotates. 
Following the trochophore comes the veliger with its velum and with an ali- 
mentary canal in which oesophagus, stomach, and intestine have been described. 
Soon after the formation of the velum, a shell (the prodissoconch) appears and quicldy 
increases to cover the animal. Swimming is by the beating of the cilia of the velum 
(aptly termed propeller by one waterman). The shell is of the type known as straight- 
hinged, although the hinge line really is concave. (Fig. 21 h.) Belding obtained this 
