SAEGEXT : THE OPTIC EEFLEX APPARATUS OF VERTEBRATES. 147 



ments are in most cases given for three regions in the course of the 

 fibre, — the 3d ventricle, the anterior part of the cord, and the posterior 

 part. 



Petromyzon marinus (40 cm.) . . 



Eaja erinacea (lOciii.) 



adult 



Squalus acanthias 



Carcharhinus obscurus 



Larval Lepidosteus (1.5 era.) . . . 

 " Amia calva (1.7 cm.) . . . 



" " " (1.2 cm.) . . . 



" Ameiurus (2 cm.) .... 



" INIotella (3 cm.) 



" Rhombus triacantlius (3 cm.) 



Menidia notata 



Naucrates ductor 



Alutera sclioepfii 



Cyclopterus lumpus 



Eupomotis gibbosus 



Prionotus strigatus 



Morone americana 



Cynoscion regale 



Pomatomus saltatrix 



Lophiatilus cliamelionticeps . . . 



Eoccus lineatus 



Stenotomus clirysops 



!Microgadus tomcod 



Salvelinus font'malis 



Palinuriclithys perciformis .... 



Lophius piscatorius 



Tylosurus marinus 



Tautoga onitis 



Opsanus tau 



Pseudopleuronectes americana . . 



Necturus maculata 



Anolis sp 



Scelopterus undulatus (8 cm.) . . 



" " (14 cm.) . . 



Alligator mississippiensis (20 cm.) . 



Eutainia sirtalis (20 cm.) .... 



Columba livia 



Mus musculus 



Third 

 Ventricle. 



1* 

 4 



2.5 



6.7 



8 



25 



1.2 



0.8 

 0.5 

 0.7 

 2.5 

 2.5 

 25 



3 

 6 



Cord. 



Anterior. 



Posterior. 



Lumen. Fibre. Lumen. Fibre 



20 

 20 

 15 



50 



40 

 45 



90 



50 

 50 

 25 

 50 

 30 

 30 

 15 

 16 



75 



30 



15 



25 

 60 



1.2 



1 



1 



3 



3.5 

 3 

 6 

 10 

 8 

 4 



2.5 

 3 

 3 



2.5 

 5 



2.5 

 4 



1.5 

 3 



2.5 

 2.5 

 1.4 



1.8 



3 



1.5 



1.8 

 1 



15 



I 3 

 6 



20 



45 



12 

 12 

 15 

 10 

 25 

 12 

 10 



4 



1.5 



2.5 



6 



1.5 



2.5 

 1.2 

 1.8 

 1.8 



o 

 O 



1.4 

 1 



