
TRANSACTIONS OF THE SECTIONS. 75 
sented vast numbers of shells, which appeared rather scattered everywhere throughout 
them, than lving in regular beds. This, together with the fact that the same species 
were found at almost every depth, made it impossible to observe levels to which the 
species could be said respectively to belong. ‘The shells, no matter at what depth 
found, were all of recent species; thus fixing the whole formation of one geological 
age. In addition to these localities may be mentioned the foundations of the town 
generally ; the whole affording a range of about twenty feet in the vertical. Eighty 
species were enumerated. Of this number not one is extinct ; five are not now living 
in the bay; seven occur so sparingly that they can scarcely be called inhabitants of 
the bay, but are rather occupiers of some very limited spot in it; while the great ma- 
jority of the remaining seventy species dwell at the distance of several_miles from their 
ancient stations, although the latter are still under water. Thus six per cent. of the 
former occupants of the harbour have left it, while nine per cent. appear in the fair 
way of doing so. The shells which occurred in the beds in the greatest numbers 
were those of the edible Mollusca. 
Dr. Mature Hamitton read a paper ‘On the Lobos Islands.””—Along the sea- 
board of Peru and Bolivia, within the Tropic of Capricorn, countless numbers of 
aquatic fowls exist, which live on fish, and whose excretions are exceedingly fertilising. 
In some localities, the number of guanos is enormous, so that when alarmed by dis- 
charges of fire-arms, or otherwise, they rise from their nestling places in such masses 
as cannot be supposed by those who have never seen these birds darkening the air 
like acloud. Guano producers change their habitation when continuously disturbed, 
but they do not permanently leave a locality which has long been frequented by them, 
in consequence of a temporary alarm; for, in such a case, they soon return to their 
old haunts, and totally abandon them only when teased by lasting annoyances. 
The ocean on the west coast of South America within the tropic, teems with fish, 
the quantity seeming exhaustless, and guanos equally abound; so that their egesta 
are gradually accumulating somewhere either on or off that desert land, and now 
have become an object sought after, not only by the Peruvian mountaineer, but by 
the merchant, shipowner, and statesman. 
On a Peculiar Organ which occurs on some of the Marine Bryozoa, and 
which appears to indicate a Difference of Sex. By the Rev. Tuomas 
Hincxs, B.A. 
Some of tle marine Bryozoa are furnished with a curious intertentacular organ, 
first noticed by Dr. Farre in his paper on the ciliobrachiata. It consists of an ob- 
long and somewhat “‘flask-shaped”’ body, which is placed between two of the arms, 
and attached to the tentacular ring. It has a wide orifice at the top, round which 
there is a play of cilia. The neck is somewhat constricted. The interior cavity is 
lined with cilia. The organ becomes narrow towards the base, and is closely united 
to the sides of the tentacles. It is constant in its position, and (in Membranipora) 
is always situated on the same side as the anal orifice. At times it is seen to be ex- 
tended considerably, and to change its form. 
It was observed by Dr. Farre on the Membranipora pilosa and Aleyonidium gela- 
tinosum (Johnston), but he was unable to determine its function. I have also met 
with it on the Cycloum papiliosum (Hassallj, and I can find no record of its occur- 
rence on any other species but the three which I have named. It is possible, how- 
ever, that it may not be confined to these, for it is commonly present on very few 
individuals, and might readily escape observation. Dr. Farre states that he was 
unable to detect any flow of fluids through it, nor could he ascertain with what parts 
the cavity in its interior might communicate. At most times nothing is to be seen 
but the regular and constant play of cilia within it and around the orifice. But in 
spring I have met with individuals furnished with the appendage, in which Sperma- 
tozoa were present in immense quantities, and have witnessed their expulsion from 
the cell through the intertentacular organ. In one instance, when examining the 
Membranipora, I observed a mass of the Spermatozoa moving upward from the lower 
part of the visceral cavity. On reaching the base of the organ, which I have described, 
