xiv REPTILES, AMPHIBIANS AND FISHES 



FIG. 



PAGE 



13. A, Development of Hylodes marUnicensis. 1, embryo seven or eight 



days old; 2, twelve days old; 3, young just hatched. B, Stages 

 in metamorphosis of Common Frog. 1, tadpoles soon after 

 hatching ; 2, tadpole with external gills, from above ; 7, young 

 frog l8 5 



14. Midwife Toad (Alytes obstetricans) ; a, male with eggs ; b, female . 192 



15. Hyla goeldii, a tree-frog carrying eggs on its back ; a, from above ; b, 



from side; c, young when hatched ...... 194 



16. A, Rhinoderma darwini, external appearance. B, A specimen of the 



same with the gular sac cut open showing contained embryos . 197 



17. Development of Crested Newt; a, b, stages within the egg; c, d, e,f, 



stages of the larva magnified ....... 200 



18. Skull and gill-arches of Dog-fish (Scyllium canicula) with anterior part 



of vertebral column ......... 234 



19. Dermal denticles of the Dog-fish (Scyllium canicula). A, from above; 



B, from below; C, in section 237 



20. A, cycloid scale of Plaice, showing four zones of annual growth ; B, 



ctenoid scale of Sole ......... 238 



21. Development of the homocercal tail as seen in a young flat-fish. After 



Alex. Agassiz. a, youngest stage, almost symmetrical without 

 fin-rays ; b, end of notochord slightly up-turned, dermal fin-rays 

 appearing on the ventral side; c, d, end of tail more bent up and 

 reduced ; c,f, the ventral rays become terminal .... 239 



22. Skull of Salmon 241 



23. A, Holoptychius flemingi from Upper Old Red Sandstone ; B, Dipterus 



valencienncsi from Middle Old Red Sandstone .... 255 



24. Fierasfer and Holothurians. After Emery ...... 303 



25. South American Lung-fish, Lepidosiven paradoxa. A, female, B, 



male ............ 320 



26. Nest of American Bow-fin (Amia calva). After Bashford Dean . . 322 



27. Three stages in the metamorphosis of the Angler, Lophius piscatorius. 



A, newly hatched; B, some days old; C, with fin-rays developed 344 



28. Four stages in the metamorphosis of the Flounder, Plcuronectes flcsus. 346 



29. Variation in number of dorsal fin-rays in a sample of North Sea plaice . 360 



30. Microscopic structure of Luminous Organs of Fishes. A, Section of 



pearl-like organs of Myctophum. After von Lendenfeld. B, 

 Section of head of Ipuops. After Moseley. C, Portion of same 

 more highly magnified. D, Longitudinal section of lateral line 

 of Halosauropsis. After von Lendenfeld ..... 424 



31. Microscopic Structure of Luminous Organs of Fishes. A, Surface view 



of the three partially united postero-lateral organs of Sternoptyx 

 diaphana. B, Longitudinal section of same. After von Lendenfeld. 



C, Section of phosphorescent organ of Porichthys notatus. After 

 Greene , . . 427 



32. A, the Hag-fish, Myxine glutinosa. B, Californian Hag-fish, Bdello- 



stoma stouti. C, River Lamprey, Petromyzon fluviattlis . . 447 



