PARTULA FRAGILIS. 33 
classes may be distinguished, as darker buff, buff, and white, whose varying numbers 
in the collections from the several localities are given in table 10. The second of 
these is the central color group, because all of the adolescents are of this kind (adults, 
figs. 13 and 15; adolescents, figs. 17 and 18, plate 11). By subsequent darkening, 
and especially by the widening of the darker transverse streaks, the first-named 
color form is produced (fig. 12, plate 11). Decortication throughout leaves the entire 
shell white (figs. 14 and 16, plate 11), save for the minute patches of cortex which 
still adhere irregularly over the surface. 
A parietal tooth is never formed, and not even a trace of this structure has been 
observed in the shells which provide the basis for the present account. 
On a close examination of the snails of various ages, the astounding discovery 
was made that reproductive ability was manifested by individuals whose shells 
had not yet formed the flaring lip which is elsewhere the sign of maturity. The 
statistics of fecundity (table 11) have a peculiar interest in this case. They show a 
relatively low rate of productivity as compared with other species; yet every 
“adult” snail wherever found was gravid. Among the “adolescents” whose shells 
measured over 12 mm., 13 out of 15 were also gravid and their collective rate of 
fecundity proved to be only slightly less than that of the snails with completed 
shells. Individuals below 12 mm. in length were uniformly barren. 
TABLE 11.—Partula fragilis, Guam. Statistics of fecundity. 


















Embryonic contents. 
Average 
Series. Records.| Gravid. for 
Eggs. | Young. | Total. gravid. 
“ Adults”’: 
Barrigatda aca. sec. sack 13 13 17 1 18 
CON eas hs Bio 13 13 23 1 24 
Whole series: . s.562 3/5025 36 36 56 6 62 
““Adolescents’’: 
(vers L2 min iecc, eres ae 15 13 £7 5 ZZ 
Tout. chek ee 51 | 49 73 11 84 

The shells of the embryonic young (fig. 19, plate 11), attain a length of 4 mm. 
before the animals emerge to the outer world. The eggs possess a tough capsule, 
fully impregnated with calcareous salts; and in this latter respect fragilis differs from 
all other species of Guam. In their great size, the eggs of this species are also 
unique; the length is about 4.2 mm. and the transverse diameter is 3.3 mm. One 
partly-grown individual with a shell 12.9 mm. in length, contained one young snail 
and two eggs whose combined lengths were 11.5 mm.—truly an astonishing bulk 
for the reproductive products of so small a snail. 
