PARTULA RADIOLATA. 55 
representative; many of the individual associations are scanty, it is true, but their 
data are given in order that all observations shall be recorded. The gravid adults 
amounted to 86 per cent of all, and they yielded 3,502 eggs and 1,909 young snails, 
or a total of 5,411; thus the average embryonic contents of the bearing animals were 
4.12, while the figures are 3.55 for the entire series. The latter datum is an index of 
the reproductive rate of the whole species during the period of collection and 
observation. 
In other species, where the embryonic capsule is provided with calcareous 
substance, this material is withdrawn as the young snail forms its shell, thus leaving 
the capsular wall transparent; hence there is a relatively definite transition from the 
“ego” to the “young” period. In the case of radiolata no such guidance is afforded 
for the classification of the brood-pouch material into the two age-classes; while this 
classification is therefore arbitrary in a sense, it is made on the basis of long experi- 
ence with thousands of young specimens in other species, and the determinations 
are substantially accurate. 
TABLE 22.—Partula radiolata, Guam. Aberrations in the order of 
embryonic contents. 



: Number of ¥ 
Locality. liga nces’ Embryonic contents. 
Weed Ome tect ete ciees oven 1 @, Vive ¢ 
1 Yo ¢ 2Y~ ee 
1 View Cen O ee. C6 
Vi PIOWEN 7... cutest» ane aus aa. 1 e Wve eee 
bY BSiacry fo Neer eran eee oe ee 1 Coe vare 
Fonte. bs x Aree. os, oe 1 éy 2¥> Oe 
CADTaAS | CASCicas «eae cna. « 1 Ce Vea Choe 
z e a¥" en eee 
Cabras, WeSst.jc scien 3 so sige 1 VoTen YY | &. ee € 
1 ew. exe Lessee 
SOLOUE ee ataiee sh eck eke het 1 ey é 
1 en Yale. ve 
1 Vv" ‘er wyrw ‘ent "e7 € 
Umatac Salonga.......... 1 Vee. St -¥o ce eG ,e Ve re 
Umatac Madog ie incu ot. ye a rr ee 
1 eC evs, Ga vere 
2 Cm Vol 6.46. eG 
1 Yo re eye er ee 


Before proceeding to the circumstantial discussion of the returns, a minor 
matter of some interest may be mentioned. This is the observation that occasion- 
ally certain of the capsules within the brood-pouch or uterus contain no embryos; 
either an egg is present which is not fertilized, or a capsule is fully formed without 
receiving a zygote. In all, there are 23 such instances among the 1,313 gravid 
snails. Doubtless there were others which escaped notice, because it is only when 
young snail embryos are also present in a position of later formation that the 
so-called “anachronisms”’ are evident. The term “anachronism” is not properly 
