584 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Mussel. He divides his account of its macroscopic anatomy under the 
heads of (1) renal duct and ureter, (2) renal sac, (3) tip of organ, (4) its 
loops, and then deals with its blood and nerve supply. Its microscopical 
characters are first treated of in relation to the structure of the walls, 
the epithelial cells, and the sensory epithelium being next dealt with. 
The walls of the organ are found to be composed of a homogeneous 
ground-substance with which are associated various kinds of connective- 
tissue-cells. These form a delicate wall for the true kidney and a firmer 
partition between it and the pericardium. Smooth muscle-cells are scat- 
tered between the connective cells. The apices or tips are formed of firm 
bandlike connective and muscular cells which are arranged circularly 
and longitudinally. Around the ureters the fibres are chiefly arranged 
in a circular manner. 
The epithelial investment consists of three kinds of cells; the 
excretory with scattered flagelliform cilia, which are found in the whole 
of the organ except the tips and ureters ; in these last there are cylindrical 
cells with closely set cilia ; at the renal end of the tips there are cells 
with extraordinarily long cilia. 
The author concludes with some observations on the morphology 
and physiology of the organ of Bojanus. In the Acephala the organ is in 
close relation with the posterior adductor and the gills ; in those species 
(e. g. in Pecten and Cardium ) in which the longitudinal axis is short, 
the organ is saccular and lies in the space between the pericardium 
a id the posterior adductor ; but when the body is long, as in Anodonta 
or Mytilus , the organ extends almost the whole length of the gills; 
these facts lead us to suppose that the primitive position of the 
organ was between the pericardium and adductor. The history of its 
development shows that the first portion of the organ was the ciliated 
funnel or tip of the kidney ; the second, the true kidney formed of sac 
and loops ; the various coils seen in Gyclas are in Anodonta replaced by 
coils which are simpler but rich in folds. The points made out by 
Ziegler are intelligible if we suppose that the ureter has an ectodermal 
origin. 
There can be little doubt of the renal function of the organ of 
Bojanus, but it is of interest to inquire whether it has any other functions 
— does it assist the circulation of the pericardial fluid or does it intro- 
duce water into the pericardium, and so into the whole vascular system ? 
The former is possible, but the arrangement of valves is such as to 
prevent the entrance of water from without. 
Repair of Test of Anodon.* — M. Moynier de Villepoix has made some 
experiments on the repair of the test of Anodonta ponderosa ; he has 
removed from the edges or sides of the shell pieces sufficiently large to 
allow observation of the modifications which supervene. The subjects of 
the experiments were put in (1) a basin which communicated with the 
stream from which they were taken, or (2) water from the stream which 
was renewed every two days, or (3) water entirely deprived of carbonate 
of lime. In all cases the animal reformed the parts which had been 
removed. 
In those in which the edge of the shell was removed the epidermis 
* Comptes Rendus, cxi. (1890) pp. 203-6. 
