1922. | Indian Science Congress. 1.8.C. 91 
those that are induced by the presence and irritation of pone foreign 
a, @ grain 
ody, usually a dead ina larva, a grain of r intrusive 
particle, and th that a nucleus of pivourasid ike substance 
derived from the oyster’s own tissues. Thef s8, according 
author’s investigations, comprises the sale of the larger cyst-pearls,— 
2 se supnee arls—the Jatter of the smaller ones of this description, 
itute by far the larger ancien: of cyst-pearls hi 
pata elased e cyst the of pearl origin_in its proper perspective ; 
we see that cest 
formation than was at first velerse are nevertheless the most important 
rg 
f supreme importance from the secant rape commercial standpoint. 
The process of pearl dn ion in the case of these two kinds of ho 
pearls and also in that of muscle pearls we detailed as deduced fr 
experiment ntal work on this subject 
scle pearls are those that ¢ form paid: Hoe Sade me insertion of 
the pallial and other m tele attached to shell ; he columnar 
nature of their pseudo-nuclei, we infer on their initial Ait is dne to 
the dislodgement of a tiny particle of hypostracum from the surface of 
1 
— — compound pearls. Usually only one layer of hypostracum 
o rios- 
8 laid down, the —— layers being compose cre 
‘a acal la seliang 3 $ not usually laid ‘down around the original nucleus as is the 
case in cyst- pearls uae by the irritation of an intrusive foreign body. 
Notes on the Genera Bullinus and Physa in the Mediter- 
ranean Basin (Mollusca Pulmonata).—By N. ANNAN- 
D . 
tes are given on the appearance and sae sas! of Bullinua 
truncatus and of Physa semiopaca and P. acuta as obse ved in the south 
of France, —— and Egypt. A vonpaeaties table o yer m: 
added, specially stress being p the existence of red blood in 
the: latter and its absence in the otto 
On the adi of some Turbinellidae—By EB. VxeD8N- 
BUR 
ae well-defined modifications ee ae successive 
m certain series of fossi il 
the oli i r miocene 0 of wes . - 
he —— seat: middle and uppe ects hesitation 
be omi , the er- 
rticular series is extinct along 
ahs The Sn 7’. pirum belongs to a separ- 
ate branch of foreign origin. 
Amongst the Turbinelidae — _— Tertiary has cogs yielded 
oo forms of Melongena pugilin _ paradisiaca melong- 
