NEW POINTS IN THE STRUCTURE OF AMPHIOXUS. 263 
lying now in close apposition and parallel to the base. This 
is explained by the diagram (fig. 1). The remarkable 
fig L 
e M4 Cc 
Fic. 1.—Diagram to illustrate the change in the lumen of the metapleur 
of Amphioxus, consequent upon distension of the atrial chamber. 
variety of connective tissue by which the outer (dorsal) wall 
of the latero-ventral lymph space is formed, which Wilhelm 
Miiller compares to erectile tissue (see Stieda, fig. 4, y), is 
possibly connected with this periodical distension which 
must yecur at every breeding season. In the living speci- 
mens which I examined last year the latero-ventral folds or 
metapleura (which are obvious enough when the sexual pro- 
ducts are of half size) did not cover in the ventral integu- 
ments, but stood up on each side of it, leaving a broad area 
absolutely exposed between them. On placing such speci- 
mens in alcohol the water in the atrial and other cavities is 
removed and the whole organism shrunk, and then it is that 
the metapleura (latero-ventral, lateral or marginal folds) 
project inwards to form an incomplete subventral canal. 
By the side of Kowalewsky’s statements as to the ejection 
of the eggs (‘ ausgeworfen’) is the word he uses) from the 
mouth of Amphioxus, I cannot admit Prof. Wilhelm Miiller’s 
conclusion, who says that the eggs must pass out by the 
atrial pore, together with the water from the branchial 
sac. He adduces as a reason that the branchial slits are too 
fine for the eggs to pass in between them. It appears to me 
that they are not too fine, especially in the anterior region, 
and that the eggs probably do escape by the mouth or else 
(and more probably) by the two apertures placed one on 
each side of the mouth, which Johannes Miiller first de- 
scribed (PI. III, fig. 4, d, Berlin Akad., 1842) and which no 
one appears to have seen since. I have recently found these 
apertures, as to the existence of which there could scarcely 
be a doubt in the face of the positive statement and drawing 
+s ° : 5 
of Johannes Miller; and I will now direct attention to 
them. 
Hyoidean apertures (J. Miiller’s pores of the lateral 
canal).—The apertures in question are placed one on either 
