6 DR. J. F. GEMMiLL OX [May 12, 



biilars (PI. I. fig. 1). The fifth nerves emerge through deep 

 grooves between the trabeculte and the auditory capsules, while 

 the vagus and glosso-pharyngeal nerves pass out together through 

 a foramen in the cartilage connecting the auditory capsules with 

 the parachoi'dals. A single opening in the floor of the capsules 

 on either side gives passage to the internal jugular vein and the 

 facial nerve. The nasal cartilage is connected with three pairs of 

 bars: (1) the trabecula3 cranii, (2) the palatoquadrates, and (3) 

 the supraorbitals. These last pass backwards along the dorso- 

 lateral angles of the brain to join the anterior part of the 

 auditory capsules on either side. Over the pineal body and the 

 third ventricle the supraoi'bitals are connected together by a 

 bridge of cartilage, but no such legmen exists over the cerebral or 

 optic lobes, the spaces left uncovered being the anterior and the 

 middle fontanelles (PI. I. fig. 2, /I, /2). The hyomandibulars 

 are connected with (1) the outer aspect of the auditory capsules, 

 (2) the posterior ends of the palatoquadrates, and (3) the inter- 

 hyals. The Meckelian bars are slender, and meet below the 

 mouth in a symphysis. Posteriorly they articulate with the 

 palatoquadrates, but not with the hyomandibular or interhyal 

 cartilages. In the hyoid arches, glossohyals, hypohyals, cerato- 

 hyals, and interhyals can be distinguished. The branchial 

 cartilages are five in number, and have the usual forms and 

 relations. The pectoral girdle is represented by vi comparatively 

 short bar of cartilage on either side — the coraco-scapular — and is 

 far from being a complete arch ventrally. The limb-cartilage is 

 an unsegmented plate continuous with the coraco-scapular bai-. 

 The notochord consists of pith-like tissue surrounded by a very 

 firm capsule, and its anterior end is embedded in the fused para- 

 chordal cartilages. In the position of each future vei'tebra there 

 are four cai'tilaginous nodules, placed respectively at the dorso- 

 lateral and ventro-lateral corners of the notochord, and prolonged 

 into processes for the neural and hsemal arches (PI. I. fig. 7). 



The anatomy of the central nervous system and of the organs 

 of special sense, and of the heart and blood-vessels, is, with certain 

 differences in the relative size of parts, practically the same as in 

 the adult condition. As regards the aortic I'oots, it may be 

 stated that the first root, i. e. the first branchial vein, gives ofi" 

 the hyoid and carotid arteries and then passes backwards to join 

 the second root. The resulting trunk bends inwards to the middle 

 line, and, meeting with its fellow from the opposite side, forms 

 the upper part of the aorta. This part is next joined on either 

 side by a trunk formed by union of the third and fourth roots. 

 The carotids pass forward beneath the parachordals and, traversing 

 the pituitary space from below, reach the base of the brain. The 

 hyoid artery arises from the first aortic root at its ventral end, 

 perforates the hypohyal, runs up along the hyoid bar, and, after 

 passing through a foramen in the hyomandibular, is continued 

 mainly into the pseudobranch. The efferent vessel of the pseudo- 

 branch passes forwards and inwards, traverses the pituitary space 



