56 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Table 17. — The rate of development of the embryo at Woods Hole. 
No. 
D.y, 
Hour. 
Tempera- 
ture of 
water. 
Age 
of egg. 
Stage of development. 
Remarks. 
1 (1) 
1890. 
July 30 
1.45 p. m. 
°F. 
72 
Hours. 
8(?) 
Folk unsegmentod 
2 to 4 cells present. 
1 (2) 
...do ... 
6.00 p.m. 
72 
12J 
do 
1 (3) 
...do .... 
lO.OOp. ill. 
72 
16* 
do 
1 (4) 
July 31 
10.00 a. m. 
72 
28£ 
Segmentation of yolk. 
Few eggs only, with yolk nnsegmented. 
1 (5) 
...do... 
2.00 p.m. 
72 
32* 
do 
Very tew eggs still with yolk unsegmented. 
1 (6) 
. . .do 
6.00 p. m. 
72 
30* 
do 
Several stages of yolk segmentation, some 
1 (7) 
Aug. 1 
9.30 a. in. 
72 
51| 
do 
eggs with about 30 segments ; others with 
very small and numerous cells; in a few 
.eggs yolk still unsegmented. 
Majority of eggs with at least 160 segments ; 
1 (8) 
Aug. 2 
12.00 ru. 
72 
m 
do 
some with irregular segmentation; some 
with yolk nou-segmented. 
Majority of eggs with periphered layer of 
1 (9) 
Aug. 3 
11.00 a. m. 
72 
100J 
Invagination 
very small cells ; rarely an egg with unseg- 
meiited yolk. 
Majority of eggs in this stage. 
2 (1) 
18S9. 
July 11 
5.30 p. m. 
68 
Segmentation of yolk. 
Late stage, about equivalent to 1 (7) above: 
2(2) 
July 12 
9.30 a. m. 
68 
16 + 
do 
cells not quite superficial. 
Protoplasm generally at surface, aud cells 
2 (3) 
July 13 
1.00p.m. 
69 
43*+ 
Invagination 
most numerous ou one side of egg. 
2 (4) 
July 14 
5.45 p. m. 
69 
72* + 
do 
Pit at surface. 
2(5) 
Jnl'y 18 
9.50 a. m. 
68 
160* + 
do 
Depression on surface very marked. 
2(6) 
July 19 
12.20 p. m. 
68 
174| + 
do 
Nauplius embryo not yet outlined. 
Table 18. — Rate of development of the embryo at Woods Hole. 
No. 
Day. 
Hour. 
Tempera- 
ture of 
water. 
Age of 
egg. 
1890. 
°F. 
Days. 
FFrs. 
3 (1) 
July 9 
3.45 p. m. 
71 
8 
3(0 
3 (2) 
July 11 
12.45 p. m. 
69 
10 
3 (3) 
July 15 
10.30 a. m. 
69 
14 
2£ 
3 (4) 
July 17 
12 m. 
70 
16 
3J 
3 (5) 
July 22 
12 ill. 
70 
21 
'ii 
3 (6) 
...do .... 
10.30 a. m. 
69 
24 
2* 
3 (7) 
July 27 
70 
26 
24 
3 (8) 
July 29 
5 p. m. 
71 
28 
8J 
3 (9) 
Aug. 3 
10.30 a. m. 
72 
33 
2| 
3 (10) 
Aug. 12 
12.30 p. m. 
72 
42 
164 
3 (11) 
Sept. 1 
61 
3 (12) 
Oct. l 
91 
3 (13) 
122 
3 (14) 
152 
1891. 
3 (15) 
Jan. 1 
183 
3 (16) 
Feb. 1 
211 
3 (17) 
Mar. 1 
242 
3 (18) 
Apr. 1 
273 
3 (19) 
May 1 
303 
3 (20) 
J une 1 
334 
Stage of develop- 
ment. 
Invagination 
Egg-nauplius I 
. . . -do ! 
I 
do 
Post-nauplius 
Remarks. 
Pit at surface very conspicuous. See cut 25. 
In some eggs, second antenn® not budded. 
Second antenn® bifid; thoracic abdominal 
fold formed. See cut 31. 
Late egg-nauplius. See cut 32. 
4 to 5 pairs of post-mandibular appendages ; 
tip of “tail” conspicuously forked; optic 
disks lobular. Cut 34. 
Optic lobes very large; telson overlaps 
brain ; 6 or 7 pairs of post-mandibular 
appendages; antenn® and telson tipped 
with rudimentary set®. 
Telson reaches base of optic lobes. 
Eye pigment present for about 24 hours. 
'Cut 35. 
Eye-spots crescentic or semicircular; telson 
overlaps bases of optic lobes. 
Eye-spots oval; telson considerably behind 
optic lobes. 
See drawing, cut 36. 
See drawing, cut 37. 
See drawing, cut 38. 
Larv® hatching out. 
The lobster (No. 3, table 18) which laid eggs about July 1, 1890, was kept under 
observation at the Fish Commission station at Woods Hole for a period of 11 months 
or 331 days, until June, 1891, when, as we see, the eggs had begun to hatch. Under 
natural conditions the period of incubation of the summer eggs at Woods Hole is 
nearer 10 mouths — (from July 16tli-August 15 to May 15-June 15). 
