PLATE 8 
Fig. 40 is from a 7.3 mm. embryo. The section passes through the posterior 
extension of the epibranchial placode of VII and the posterior extension of the 
primordium of the sensory line lying dorsal to it. Thissection contains the an- 
terior end of the geniculate ganglion and lies four sections posterior to fig. 39. 
Fig. 41 from an 8 mm. embryo, passes through the extreme posterior portion of 
the contact of hyoid gill pocket with the ectoderm. It shows in addition to the 
differentiation between ectoderm and endoderm the fact that the geniculate gan- 
glion sometimes extends forward over the phyarngeal gill pocket. The primordium 
of the sensory line lies well dorsal to the ectodermie gill thickening. 
Fig. 42 from an 8 mm. embryo, shows the first section posterior to the point 
where the hyoid gill pocket withdraws from the ectoderm. The epibranchial 
placode is cut through its anterior end. The small mass of cells lying between 
placode, endoderm, and geniculate ganglion may belong either to the placode or 
to the ganglion since the ganglion has a rather indefinite outline. 
Fig. 43 from an 8.3 mm. embryo, shows the maximum size of the placode at this 
age. The indefinite outline of the geniculate ganglion at this stage renders the 
line of separation between the placode and the geniculate ganglion difficult of 
determination. 
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