PARTULA GIBBA, GUAM. 71 
TABLE 42.—Partula gibba, Guam. Apra, West Central, and Southwest Regions. 
MEAN VALUE. 












Shell. Aperture. Length aper- 
Series. BN Co ee ee ee ture = length 
shell, propor- 
Length. Width. Proportions. Length. Width. Proportions. tions. 
Orote: mm, mm, p. ct. mm. mm, p. ct. Pp: ct. 
oS. Gee ee 19 | 16.6763 +.0644| 12.1210+.0687| 72.3421+.2573|} 9.7421+4.0433) 7.2684+.0417| 74.5526+.2432!58.1842+.1813 
Agat: 
iOS ae 6 | 16.7000+.1952| 11.6667 +.0922| 69.1667+.5192) 9.7000+.1189} 7.1000+.0841| 72.8333 +.4943)|57.5000 +.3179 
Salifan: 
Bicoloroecicn fcc.» : 1 | 17.7500 12.1000 67.5000 10.1000 7.3000 72.5000 56.5000 
OAL as SR 85 | 17.3371+.0510} 12.0647 +.0342| 69.6294+.1298| 9.9470+4.0290| 7.3282+.0224| 73.6059 +.1299|57.3471+.1037 
Umatac Salonga 
Shel: 3 Se eee 7 | 17.36434.1059| 11.5572 +.0534| 66.3572+.4400} 9.8429+.0230) 7.0429+.0357| 71.7857 +.4859|56.07144.2676 
Umatac Pajom: 
OS aoe 9 | 17.7500+.0779| 12.3000+.0670} 69.2777 +.2956| 10.0555+.0591; 7.4555+.0412| 74.1666 +.3671|56.5000 +.2596 
Umatac Madog: 
BRCOIOR ei aes cici 3 4)0's 6 | 17.6500 +.0616) 12.0000+.0527| 67.83334.2052} 9.8333+.0757| 7.2667+.0587| 73.8333 +.3784/55.3333 4.2938 
Merizo: 
ed Ek Aloe eee 1 | 17.4500 12.5000 71.5000 10.1000 7.3000 73.5000 57.5000 
| 
STANDARD DEVIATION. 
Orote: 
wars sar sono pen ieee 19 0.4165+.0455| 0.4444+.0486) 1.6627+.1819) 0.2797+.0306| 0.2696+.0295| 1.5719+4.1719) 1.1721+.1282 
Agat: 
mnibkella scare ete sare. 6 .7089 --.1380 .3349+.0652| 1.8856+.3671 .4320+.0841 3055 +.0594| 1.7951+.3495|1.1547 4.22448 
Salifan: 
BSA cect ears, <u + Fh yh ee Bast Gru Sects |e aware Ae on auction EW ce eect red | ei An ey Racca eR i | i | 
STEEL Re. gh diate N averske es 85 .6979 +.0360 .4675+.0242} 1.7743+.0918 .3960 +.0205 .3070+.0518) 1.7758+.0918) 1.4148+.0733 
Umatac Salonga 
cra Sy Oy ie Ro eee 7 .4155+.0749 .2096+.0377) 1.7262+.3111 .0904 +.0162 .1400+.0252) 1.9059+.3436) 1.0498 +.1892 
Umatac Pajom: 
oot Aa oe Se 9 -3464+.0551 .2981+.0474; 1.3147+.2090 .2629 +.0418 .1833 4.0291} 1.6329+4.256 | 1.1507+.1835 
Umatac Madog: 
BICUIOES Kaden Aang Se ws 6 .2236+.0435 .1915+.0372 .7453 4.1451 .2749 +.0535 .2134+4.0415| 1.3744+.2675| 1.0673 +.2077 
Merizo 
bicolor... coi dead o) s eee ee rene Wt OP ee a NT NS eats, SECS Lat od ere, sta wrens dye Miaeterl ata e Robe teins opep a ['d Sitaraiehe Wild Be nei es vie 8 aise wa. 



within the wall of the capsule, the young snail may grow until its shell is 4.5 mm. 
in length before it is born. 
The total number of adults available for the record of embryonic material is 
2,384, as only 20 were omitted for various reasons; the statistics of their contents 
are given in full in table 45. The proportion of gravid individuals in the whole 
collection is 85.8 per cent, which is almost exactly the same as in the radtolata 
series. As the 2,046 gravid adults yielded 6,053 young and eggs, the reproductive 
rate of the entire series of gibba is sensibly lower than that of radiolata, namely, 
2.54 as compared with 3.55. This difference might be variously interpreted; 
it may mean that the breeding seasons of the two species do not coincide, and 
that radiolata was at the height of its activity at the time of investigation, while 
gibba had not fully entered or had recently completed its own cycle of reproduction. 
Again, it may be that radiolata is now developing in greater relative numbers 
than before, or conversely that the rate in gibba is declining. Finally, it is possible 
