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 haemal 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 

 quadricomis, when -£% 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, T V 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 haemal 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 haemal 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 haemal 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 likewise ossified. All 

 the structures mentioned have become more ossified at the beginning of May, the haemal 

 arches meeting posteriorly to enclose the artery and support the interspinous elements 

 of the median ventral fin with its fin-rays. The haemal 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 haemal 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 lamellae leave the 

 various ossified structures connected with the vertebral column, as Grassi t 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 unsegrnented cartilaginous tube Balfour found round the notochord of Elasmobranchs. 



t "Lo suiluppo della colonna vertebrale ne pesci ossei" {Mem. del dott. Battiste Grassi ; Atti d. R. Accad. dei 

 Lincei, seri. 3, vol. xv. pp. 311-337, Taf. i.-viii.). 



