906 PROFESSOR W. C. M‘INTOSH AND MR E. E. PRINCE ON 
hyaline coat, having the form of a translucent ring, in transverse section, separated by an 
interval from the inner limiting cells of the chorda itself. The neural arch is imperfect at 
this stage; but the heemal arch, formed of the same hyaline matter, is complete in the anal 
and caudal regions. It is remarkable, that in the tail, the elements of the neural arch are 
formed of cartilage, upon which hyaline matter appears as a thin shell; but anteriorly the 
arch is formed by hyaline outgrowths solely. A similar condition is exhibited by Cottus 
quadricornis, when 25 inch in length, the cartilaginous outgrowths destined to unite as 
the neural arch in the caudal trunk, having at first a plate of hyaline matter deposited on 
the outer surface only. In the post-larval Labrus, 3%, inch long, while the anterior part 
of the spinal cord is protected incompletely by the developing neural arch, consisting of 
hyaline basal stumps, and an independently formed hyaline neural spine, bifurcate below, 
the posterior portion of the cord in the tail is still enclosed merely in the membranous 
chordal sheath, destitute of any more permanent element than the rudimentary neural 
spine, which consists of two approximated plates of hyaline matter, clothing a strand of 
connective-tissue. This strand forms dorsally a knob, which is deeply stained in the 
microscopic preparation, and continues to the base of the dorsal fin (in this species 
characteristically lengthened), where a second pair of hyaline plates are developed, viz., 
the rudiments of the terminal fin-rays. The hemal arch below is complete, and encloses 
what appears to be a mass of cartilage, so that it is really a solid ventral process, below 
which pass the caudal artery and vein. In the caudal fin the same features are seen, but 
the connective-tissue strand which passes down from the hemal arch is clothed by hyaline 
matter, two lengthy plates of which form a large hypural, and upon their outer surfaces 
a diagonally directed muscular band is inserted on each side. Each muscle is attached to 
the corium about the level of the heemal arch, and passes obliquely downward. 
The cellular external region of the notochord in Anarrhichas is rendered conspicuous 
by the appearance of the definite hyaline ring above mentioned. A similar ossification 
proceeds in the dorsal fin-rays, in fact, they appear to commence as hyaline bars; but 
the interspinous elements seem not to do so, The neural spine is hkewise ossified. All 
the structures mentioned have become more ossified at the beginning of May, the hemal 
arches meeting posteriorly to enclose the artery and support the interspinous elements 
of the median ventral fin with its fin-rays. The heemal arches in the region near the 
caudal become elongated, the posterior pair being also greatly flattened, for the support 
of the caudal rays.* At a still later stage, towards the end of May, the hemal spines 
have frequently between them a transverse row of cartilage-cells, apparently binding them 
together towards the tip, the evidence of a series of sections showing that amalgamation 
has taken place. The ossified sheath of the notochord is now brittle, and frequently gives 
way under the knife of the microtome. At this stage no special lamelle leave the 
various ossified structures connected with the vertebral column, as Grasstt shows in 
* The firm hyaline ossification here mentioned is by the process called ectostosis. When surrounding the chorda 
in the wolf-fish, it recalls the unsegmented cartilaginous tube BaALrour found round the notochord of Elasmobranchs. 
+ “Lo suiluppo della colonna vertebrale né pesci ossei” (Mem. del dott. Bartiste Grassi; Atti d. R. Accad, det 
Lincei, seri. 3, vol. xv. pp. 311-337, Taf, i—viii.). 
