106 HERBERT E. DURHAM. 
parts are slung by lamine of connective tissue: for those spaces 
which surround the peripheral parts of the system Ludwig’s 
term perihemal canals will be retained. The canal in 
which the dorsal organ is contained may be called the axial or 
dorsal (perihemal) sinus, the “ schlauchformiger Kanal ” 
of German authors. Water-tube, as recommended by Dr. 
P. H. Carpenter, will be used for the “‘ stone canal” or ‘canal 
de sable; ”? and madreporic tubules for the appropriate portion 
of the water vascular apparatus. 
Of the naked eye appearance of the dorsal organ in A. 
rubens it would be superfluous to say more than that it 
tapers towards its oral end, and is of a pale colour which varies 
in different specimens (brownish to purplish). Examined with 
a low power, in the living state, it has a lobulated appearance, 
and is seen to consist of a number of strands of tissue, upon 
which there may be variously sized clear transparent swellings 
(fig. 4). Under a high power the following can be seen :—1l. 
Fibrils running longitudinally. Whether any of these are 
contractile, authors are disagreed ; anyhow, the organ becomes 
shorter when removed, and exhibits contractions when irritated 
witha needle. Kowalewsky (No. 40) says, ‘‘ Bei den Kchiniden 
habe ich deutliche Kontraktionen der ovoiden Driise gesehen : 
wenn es noch keine regelmassigen Pulsationen waren so 
waren es doch wiederholte Zusammenziehungen des ganzen 
Organs.” 
2. Large numbers of cells similar to the leucocytes seen in 
the ccelomic fluid, &c., some containing small granules, and 
sometimes with pseudopodial processes projecting from the 
surface of the strands of the organ, exactly like those of certain 
free corpuscles ; others contain larger spherules, and have been 
called spheruliferous corpuscles. 
It would be supposed from most descriptions that the surface 
was freely ciliated; this I have not found to be the case, there 
is very slight movement amongst particles floating in the 
neighbourhood. At first I thought the pseudopodial processes 
were cilia, but careful observation showed that this was not 
the case; the individual cilia are few and scattered, and are 
