“NEW POINTS IN THE STRUCTURE OF AMPHIOXUS. 261 
which the genital glands are placed. In each pharyngo- 
dorsal coelom at its commencement a deeply pigmented canal is 
seen in section appearing as a thick irregular ring, lined 
within by a dark brown membrane, the pigment granules of 
which are disposed precisely as in the atrial tunic. The 
ring thus seen in the section is attached to the body wall 
(epipleur) by one side, the rest of the ring projecting freely 
into the pharyngo-dorsal ccelom. As far as Ihave yet been 
able to ascertain, this canal is open at each end, posteriorly 
communicating with the atrial chamber, anteriorly consider- 
ably contracted and possibly closed. 
The pigmented canals are constant in position and form. 
I have found them in several specimens always in the same 
place and equally developed both in males and females. 
There is not much difficulty in tracing a similarity of rela- 
tions between the pigmented canals of Amphiorvus and a 
single pair of the funnel-like canals which build up the renal 
organ of higher Vertebrata. On this subject I shall add 
some reflections below. 
Lateral folds (metapleura), lateral canals, ventral canals, 
and plaited epithelium.—The lateral canals have acquired 
special interest and importance from the suggestion by Pro- 
fessor Haeckel that they represent the primitive renal ducts 
of higher vertebrates. 
Stieda figures these canals—the space in the lateral or 
marginal fold (metapleur) which stands up as a ridge on 
each side of the ventral area of Amphioxus—as seen in 
transverse sections; but they are somewhat over-distended 
in his specimens by end-osmotic action. Professor Huxley is 
inclined to deny their existence, and it certainly is the fact 
that in specimens preserved in absolute alcohol they are 
shrunk by ex-osmotic action to a very small size. Professor 
Wilhelm Miller, of Jena, asserts their existence and speaks 
of them as lymph spaces. This appears to me to be the 
correct view of their nature, and it would be better to cease 
speaking of them as ‘canals,’ since they have no openings 
either before or behind, but are simply loose spaces in the 
subcutaneous connective tissue. That they have a real 
existence is proved by the presence in them of coagulated 
serous fluid, and by other facts to be detailed below. 
The ventral canals of Stieda’s memoir, (7” 7’) have a dif- 
ferent nature. ‘They are undoubtedly artifact. They lie 
between the epidermis and the subepidermic connective 
tissue, whereas the lymph space of the metapleura or latero- 
ventral folds lies between two layers of connective tissue. 
The ventral canals must be given up as illusions. Professor 
