tie 
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TRANSACTIONS OF THE SECTIONS. 77 
that it answers to the mantle-cavity of ordinary mollusks; that its excessive de- 
velopment accounts for the presence of the “third tunic”’ in the Ascidian, and 
that Savigny’s comparison of an Ascidian to an inverted Patella had very con- 
siderable justice. 
The author next proceeded to detail many structural points of interest which he 
had made out in the genera examined. A minute account was given of the structure 
of the branchial sac in Boléenia, Cynthia, Phallusia, Syntethys, and other genera. 
The branchial meshes are always true apertures, generally more or less rectangular 
or oval in shape; but in one species described they were arcuated or semilunar, so 
as to give the appearance of spiral vessels in the branchial tissue. 
The structure of the dorsal folds and of the “‘ Endostyle,”’ a structure first noticed 
as distinct by the author in his memoir upon the Salpe, was minutely described ; 
and the singular and characteristic variations in form of the peculiar organ of sense 
—the “‘tubercule antérieure ” of Savigny—were pointed out. 
The “‘ Tubular System,” described in the same memoir as a peculiar and unique 
organ in Salpa and Pyrosoma, was shown to be the form of hepatic organ proper 
to, and universal among the Ascidians. 
The reproductive system exhibits remarkable and hitherto little noticed pecu- 
liarities, which have Jed the author to distinguish the simple Ascidians into Mono- 
thalamous and Dithalamous groups, the section Styela (Sav.) being the type of 
the latter. Owing to the discovery of a Marsupial Cynthia, that is, of one whose ova 
pass through all stages of their development in the Atrium of the parent, the 
author was enabled to lay some interesting embryological facts before the Section. 
The Cynthia in question has the appearance of a compound form; it does not, 
however, become multiplied by gemmation like the true compound forms, but the 
originally free, tailed larvye, adhere and become firmly united before the withering 
away of their appendages. The mass is therefore an aggregation of distinct indi- 
viduals, not one individual represented by many Zooid forms. 
The development of the muscular tissue of the tail was described, closely resem- 
bling that of the muscles of the tadpole as given by Kolliker. 
With respect to the structure of the test of the Ascidians, the author stated that 
he had verified in many new cases the discovery of the presence of cellulose in large 
quantities therein made by Schmidt, and extended by Lowig and Kolliker, and by 
Schacht. In other points, the author’s results differed somewhat from those of 
these writers ; and after pointing out what he considered to be the true structure, 
he drew particular attention to the essential identity of the test of the Ascidian with 
true bone (if for the calcareous salts cellulose be substituted) on the one hand, and 
with vegetable tissue on the other. The physiological distinction betwee: plants 
and animals, which authors have endeavoured to draw, upon the ground that the 
Ascidians do not form cellulose, but only take it from plants, seems incompatible 
with the circumstance made out by the author, that the Ascidian larve contain cel- 
lulose while they are yet a mere mass of cells contained within a structureless mem- 
brane, and totally without any organ, except the tail. 
The author endeavoured to show that the Ascidians might be divided into natural 
groups, by considering :— ; 
lst, The arrangement of the organs with regard to the axis, whence the animal 
may be symmetrical or asymmetrical, according to the relative development of the 
neural and hemal regions, and of the branchial sac; and, 
2ndly, The nature of the tentacles and of the reproductive organs. 
In conclusion, the author stated that the Ascidian type appeared to be sharply 
defined from all others, nowhere exhibiting any transition forms. 
On a New Species of Acaleph from Belfast Bay. By Grorar C. HynpMAN. 

Dr. J. D. Marsuatt exhibited specimens of the “‘ Bonaparte’s Gull,’’ “ Sabine’s 
* Gull,” “ Little Auk,” and some other fowl], all shot in the neighbourhood of Belfast. 
The specimen of ‘“‘Bonaparte’s Gull,”’ he mentioned, had been called after the Prince 
of Canino; and is the only one hitherto shot in Europe, having been obtained in the 
Lagan in 1848. It is at present in the Belfast Museum. 
