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



Plate II. 



Fig. 9. Ventral ends of the llecJcelian, liyoid, and hrancMal cartilages of the 



monstrosity illustrated in figs. 3 and 4 (see pp. 7, 8). 

 Fig. 10. Ventral ends of the MeclceUan, hyoid, and hrancMal cartilages of the 

 monstrosity illustrated in figs. 5 and 6 (pp. 11, 12). 

 Mech. Outer Meckelian bars. 



Meek.' Inner or adjacent Meckelian bars united and greatly reduced. 

 GH. Glossohyal. 

 BH. Hypohyal. 

 -LB. Ceratohyal. 



BH'. Inner or adjacent hypohyals partlj^ united. 

 iH'. „ „ ceratohyals united. 



Ill, IV, V, VI, VII. The branchial cartilages. 



Cof. Copular pieces, the anterior one being bifid. 

 Fig. 11. Transverse section of a composite pectoral fin, from a monstrosity in which 

 union took place just behind the pectoral fins (see p. 19). 

 Scap., Cor. Scapular and coracoid parts respectively of the coraco- 

 scapular bars. The ventral ends of the coracoid parts 

 are united. 

 CL. The limb-cartilages united for the greater part of their 

 length. 

 H. The rays (not cartilaginous). 

 Fig. 12. Diagram of the aorta and its roots in the monstrosity referred to on p. 9. 

 Ao'. Aorta, the two limbs uniting further back. 

 I, II, III, IV. Aortic roots, i. e. branchial veins. 

 Car. Carotids. 



Aa. Artery to pseudobranch, a branch of the 1st branchial. 

 Fsbr. Pseudobranch. 

 A.Chor. Choroidal arterj\ 



A. Ghor.' The arteries for the choroidal glands of the inner or adjacent 

 pair of ej^es. They arise bj' a single stem from the 

 middle of a vessel connecting the aortic roots on either 

 side, and go to the choroidal glands without passing 

 through a pseudobranch. 

 Fig. 13. Diagram of ventral aorta, aorta and aortic roots in the monstrositj' 

 illustrated in figs. 5, 6, 16 (see p. 13). 

 Lettering as above, with in addition : 



TA. Ventral aorta and its branches 1, 2, 3, 4. 

 Car.' Inner or adjacent carotids, giving off Aa' arteries to the inner 

 or adjacent pseudobranchs Pshr.' 

 It will be seen there are two sets of carotid and afferent pseudobranch 

 arteries, the inner sets being derived directly from the ventral aorta. The 

 ventral aorta arches dorsally in the septum between the two mouths of 

 the monstrosit}', reaches the base of the skull, and then divides into two 

 limbs which are continued backwards to join the aortic-collecting roots on 

 either side. 

 Fig. 14. Outline of central cavity of brain of normal Trout embryo. Lettering 



as in fig. 16. 

 Fig. 15. Outline of centi-al cavity of brain of the monstrosity illustrated in figs. 3, 4, 



& 9 (p. 8). Lettering as in fig. 16. 

 Fig. 16. Outline of central cavity of brain of the monstrosity illustrated in 

 figs. 5, 6, 10 (p. 12). 



C.F.B. Cavity of the hemispheres. 

 CSrdV. „ 3rd ventricle. 



COL. „ optic lobes. 



^^*- I) iter a tertio ad quartum ventriculum. 



CUh V. „ 4th ventricle. 



Spc. „ spinal cord. 



Fig. 17. Outline of transverse section of central cavity in anterior part of optic lobe 

 region of the brani illustrated in fig. 15. There are two infundibula and two 

 sets ot hypoarial cavities, while the main optic lobe cavity is single (p. 8). 

 COL. Cavity of optic lobes. 



Inf. Infundibulum. 

 Hyp. Hj'pophysis sac. 

 Hya. One of the hypoarial cavities. 



