DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 815 
sea at both surface and bottom from March to May,* and have a diameter of ‘0551 inches 
or 1375 mm. The embryo emerges from the 8th to the 10th day in April, and in 
May somewhat earlier. 
Thus those which on the 16th April presented the multicelled lenticular stage with 
the nucleated periblast surrounding the disc, next day, at 9.30 a.m., showed a still 
larger number of nuclei in this zone, which, however, at 1 p.m. had all but disappeared, 
while the blastodermic ring had increased in size. On the 18th April the blastodermic 
ring extended over a third of the surface of the ovum, and two hours later it had gained 
the equator. At3 p.m. the keel of the embryo had deepened, and faint indications of the 
optic enlargements were visible, while at 4 p.m. they were completed.t At 10 A.M. on 
the 19th the embryo was fully outlined, with five or six protovertebree. The blastopore 
had closed, and there were traces of Kuprrsr’s vesicle. At 12 noon the protovertebre 
had doubled, and Kuprrsr’s vesicle was more distinct. The invagination of the lens had 
commenced, and the alar membrane of the embryo was distinct. 
20th April.—tThe eyes, otocysts, and mesenteron (which turns to the right) had all 
made progress, and the heart showed a double-celled appearance at 3 p.m. The otoliths, 
at first very small, occurred at 4 p.m., and the pectorals were outlined. 21st April. 
The body of the embryo jerks from side to side, and the heart pulsates languidly and 
nregularly (about 3 p.m.), the contractions, however, sometimes ceasing for fifteen or 
twenty seconds. The trunk has lengthened and the caudal extremity is flexed. The 
pectorals are more distinct, and the delicate processes anterior to the fins (observed in 
most forms) still persist. The mesenteric lumen extends as far as the heart, and 
enlarges in the mid-region. The notochord is now completely crossed by intermingling 
ares. 
22nd April—the posterior region of the trunk and tail are now flexed, and the yolk 
appears to have decreased. The pectorals are well defined and pointed posteriorly, 
while the anterior margin is rounded. The liver forms a rounded process, the heart 
shows a venous end, and the pulsations are more regular (twenty-five per minute). 
Round chromatophores (black) have appeared on the head and dorso-lateral regions of 
the trunk, but they have no regular linear disposition. 
23rd April.—tThe eyes show pigment, and that over the body has increased. Three 
branchial clefts and the nasal pits are visible. The violent motions of the embryos 
indicate their advancement, and a few issued from the eggs. The empty capsules retain 
their spherical shape, though a rent passes two-thirds across their diameter. 
24th April.—Five-sixths of the embryos are still in the eggs. They present a similar 
appearance to the previous day, though the increasing complexity of the branchial region 
is evident, and four clefts are visible. Some of the chromatophores on the head are 
stellate. 
* Méprus and Herncxe state that the cod in Kiel Bay spawns from January to the end of March, but in other 
parts of the Baltic, ¢.g. Gothland, in April; op., cit. p. 233 (1883). 
+ The temperature of the laboratory was 59° F. 
