413 



it seems to be almost in contact with it. If a knife were passed 

 obliquely between the pterygoid and the suspensorium, and then 

 carried through the suspensorium to its posterior margin a little 



Fig. 9. The upper right-hand figure represents a longitudinal section of the 

 head of a tadpole just about to be hatched. The upper left-hand figure exhibits 

 a dissection of the head of a tadpole with external gills. The two lower figures 

 represent dissections of the crania of tadpoles with well-developed hinder limbs. 

 In the one, the integuments, organs of sense, &c. of the right side are taken away 

 so as to lay bare the facial cartilages and the brain. In the other the cranium 

 is opened from above, and the brain and myelon are extracted. 



The letters have the same signification as before, except My. Myelon. M. Mouth. 

 olf. Olfactory sac. op. Eye. 1. Anterior cerebral vesicle. 2. Middle cerebral 

 vesicle. 3. Posterior cerebral vesicle, la. Rhinencephalon. 1. Prosencephalon. 

 Ic. Deutencephalon, or vesicle of the third ventricle. I. II. III. IV. V. Branchial 

 arches, x. Organs of adhesion. 1. Lips. 5. Trigeminal ganglion. 7. Ganglion 

 of the portio dura. 8. Aperture for the exit of the pneumogastric. 



above the condyle for the mandible, it would divide the suspensor 

 into a proximal and a distal portion, precisely resembling those which 

 naturally exist in the embryonic fish. If the proximal division 

 ossified, it would clearly represent the hyomandibular and symplectic 

 bones. Now in the Amphibia, although the suspensor is not thus 

 divided, it ossifies very nearly as if it were, and the superior or 

 proximal ossification is the so-called " temporo-tympanic," " tem- 

 poro-mastoid," or " squamosal " bone*. 



* See this result, well worked out, by the method of gradation only, by Kostlin 

 (I c. pp. 328-332), who draws particular attention to the resemblance between 

 the suspensorium of the Amphibia and that of fishes of the Eel-tribe. 

 VOL. IX. 2 F 



