4 
PACIFIC SCIENCE, VoL XIV, January I960 
mature. Seventy-five female xanthid crabs were 
dissected in the month of June to correlate size, 
gonad development, and abdominal character- 
istics. An additional 178 females were examined 
and measurements were taken on 63 of the pre- 
mature to mature size range. These data will 
be presented for each species. 
Cycloxanthops novemdentatus: This species 
shows signs of sexual dimorphism beginning at 
the 6.5 millimeter (carapace width) size class. 
Prior to this the male and female abdomen are 
alike, composed of seven segments, the third 
being the widest segment, while the sixth seg- 
ment is less than two-fifths the width of the 
second. From about 6.5 millimeters carapace 
width the abdominal segments of the female 
distal to the third segment broaden with each 
additional molt. From the data given for this 
species (Table 1) it can be seen that there are 
two distinct classes, immature and mature, and 
a transitional submature class. 
The immature specimens are those females in 
which the gonads are undeveloped and lack ova. 
External signs of this are as follows: (1) the 
third abdominal segment is the widest of all 
segments; (2) the marginal abdominal "hair” 
TABLE 1 
A Survey of Mature and Immature Female Cycloxanthops novemdentatus* 
WIDTH 
IN MM. 
WIDEST 
AB. SEG. 
LATERAL 
"HAIR” 
LOCK 
SPERMA- 
THECA 
CONDITION 
OF OVARIES 
CONDITION 
OF EGGS 
17.2 
3 
Vs 
X 
0 
undeveloped 
— 
18.0 
3 
Vs 
X 
0 
undeveloped 
— 
19.1 
3 
Vs 
X 
0 
undeveloped 
— 
19.2 
3 
Vs 
X 
0 
undeveloped 
— 
19.4 
3 
Vs 
X 
0 
undeveloped 
— 
20.8 
3-4 
Vs 
— 
0 
somewhat developed 
— 
22.5 
3-4 
Vs 
— 
0 
somewhat developed 
— 
23.5 
3 
V4 
X 
0 
undeveloped 
— 
24.0 
3 
V4 
X 
0 
undeveloped 
— 
24.2 
3 
\a 
X 
0 
undeveloped 
— 
25.0 
3 
V4 
X 
0 
undeveloped 
— 
25.8 
3 
V4 
X 
0 
undeveloped 
— 
26.0 
3 
Vi 
X 
0 
undeveloped 
— 
26.2 
3 
Vi 
X 
0 
undeveloped 
— 
26.4 
3 
Vi 
X 
0 
somewhat developed 
— 
27.0 
3 
Vi 
X 
0 
undeveloped 
— 
28.5 
3-4 
Vi 
X 
0 
somewhat developed 
— 
30.0 
3-5 
Vi 
X 
0 
somewhat developed 
— 
31.2 
3-5 
3 /4 
X 
0 
somewhat developed 
— 
32.8 
4-5 
l 
— 
large 
ripe, gravid 
— 
32.9 
4-5 
l 
— 
large 
ripe, gravid 
lg. blastomeres 
33.0 
3-5 
l 
— 
medium 
ripe, gravid 
— 
33.3 
3-5 
l 
— 
large 
ripe, gravid 
— 
34.0 
4-5 
1 
— 
medium 
ripe, gravid 
lg. blastomeres 
34.5 
4-5 
l 
— 
medium 
ripe, gravid 
new 
35.5 
4-5 
l 
— 
medium 
somewhat developed 
— 
36.8 
4-5 
1 
— 
large 
ripe, gravid 
new 
37.0 
4-5 
l 
— 
large 
ripe, gravid 
— 
37.5 
4-5 
l 
— 
large 
ripe, gravid 
— 
38.0 
4-5 
1 
— 
large 
ripe, gravid 
— 
38.5 
4-5 
l 
— 
medium 
ripe, gravid 
new 
40.0 
4-5 
1 
— 
medium 
ripe, gravid 
— 
41.0 
4-5 
1 
— 
large 
ripe, gravid 
lg. blastomeres 
42.8 
4-5 
l 
— 
medium 
ripe, gravid 
— 
52.3 
4-5 
l 
— 
large 
ripe, gravid 
— 
* The lateral abdominal hair length is given as a fraction of the third abdominal segment length; X, present; — , absent; 
O, spermatheca empty; lg., spermatheca large, full of sperm; med., spermatheca of medium size, with some sperm. 
