GAD us. 337 



posterior border (the preopercular, opercular^ subopercular and inter- 

 opefrnlar), and joined to the quadrate by a small symplectic. Its lower 

 half forms a chain of hyoid bones which carry on their posterior surface 

 seven brmichiostegal rays. 



The four branchial arches consist of pharyngo-^ <?//-, cerato- and 

 hypobranchials., united below by the basibranchials. The pharyngo- 

 branchials fuse to form the superior pharyngeal bones already noticed, 

 and the Ceratobranchials of the fifth arch form the inferior pharyngeal 

 bones. 



The vertebral colunm consists of a large number of ajuphicoelous 

 vertebrce. The anterior are termed abdominal and the posterior are 

 caudal. All the vertebrae have complete neural arches and neural 

 spines. Most of the abdominal have also transverse processes, which 

 bear a pair of ribs and a pair of more dorsally placed so-called inter- 

 muscular bones. In the caudal vertebrae the transverse processes meet 

 below and form a complete h(e?nal arch. The median fins are sup- 

 ported on dermal fin,-rays, which rest on short ptcrygiophores and inter- 

 spinous bones. 



Appendicular. — The pectoral girdle is attached to the otic region of 

 the skull by the suprafemporal bone. There are three clavicular bones, 

 the stipraclavicle, clavicle and postclavicle. A small scapula and 

 coracoid complete the girdle ; they bear on their posterior border four 

 small h'achial ossicles (or pterygiophores), which in their turn bear the 

 numerous pectoral fin-rays. The pelvic girdle is absent, but there is a 

 large basipterygium on each side which carries \\\^ pelvic fin-rays. 



The brain is small and differs from that of the skate. 



Nervous chiefly in the large optic lobes and small cerebral hemi- 



System. spheres. On the other hand, the cerebellum is equally 

 well developed. 



The gonads are simple, paired hollow sacs opening 

 Reproductive, by short genital ducts to the exterior. They lie in the 

 abdominal cavity. 



There is as great a contrast to the skate in the development as in the 

 anatomy. The haddock lays several million eggs which are of small 

 size, perfectly transparent and buoyant. Fertilisation is 

 Development, external and the eggs are pelagic. There is a consider- 

 able amount of yolk and segmentation is meroblastic. 

 The young haddock is hatched as a transparent larva, with a large yolk- 

 sac depending from its ventral surface. After a time the young fish 

 absorbs its yolk and feeds on pelagic organisms ; still later it takes to a 

 ground-feeding habit. 



The haddock is a type of the order Teleostomi or bony-fishes, which is 

 usually contained in the class Pisces, with the Elasmobranchii and 

 some smaller orders. It is, however, evident that the two types are 

 widely divergent in numerous structural characters. 



n 



