THE ORGANS OF THE OUTER (J BUM -LAYER. 513 



The us fine, rod-like < 



their free t-iuls h-ar tinr Iri-tl'- ami aiv united into bundle 

 distinctly delimited from the I-; khf epid. 



Til. y closely resemble the sensory nerve-termination.., \\hi.-h n. 

 dantly and widely distributed in the epidermis of Fishes and other 



lower Y< thi- ln'n <>rgan* or the nervou* end-bud*. 



I'.- M i: ha- therefore named tln-m < [nictory bud*. He proceeds t 



tin- com-. -j.ii..n that, like the .similarly c-onstracted gustatory bud* 

 of the oral < i>oy are descended irm tho sensory organs 



Uited o\vr ih whole integument. The organ of sm^ 

 simply a depressed patch of tln skin richly provided with ten 

 nerve 1. ud-, \\hich. umi, i^-ing a change of filiation, has come to sub- 



re a specific sense. Tho continuous 

 olfactory epithelium of the- higher Ver- 

 ti-hrattvs ha> ari-m from the originally 

 >caU-rcl, ixilati-il olfat'tury l.ud- (tig. 

 287 rk) by a process of fusion. 1 1 

 ditVt'ivnt epithelium (fe) having rialu 

 ally disappeared. In certain >| 

 l''i.shes and Amphiliia Mich a transition 

 i-an be demonstrated. 



The further development of the .r^an 



of smell is especially chara-t-ri-iHl hy Fc.288.-Fundamat of thei 



the olfactory pits coming into ivl.:ti,,n 



canty of a human embryo ( \ 1 ! 

 with the oral cavitv. Kaeh ot them ,\ Men from below aftr 



(fig. 286) develops a fmrow >vl,i,l, ^S 



runs downward to tho upper margin M*gnlfid 12 dUunettim. 



of the mouth and recei\e> un its outer 

 >ide tlie pi -\ i.u>ly described lachrj'mal groove, coming 

 dir-ection from the eye. Nasal pit and natal furrow become deeper 

 in older embryos (fig. 288), owing to their margins protruding 

 \\ard as rid^i- and forming the so-called inner and outer natal pro- 

 cesses. The two inner nasal pro< > 



by a shallow furrow running from above downward; they tog* 

 produce a thick partition between the two olfactory pit- that in the 

 higher Vertebrates subs|u ntly becomes more and more r 

 thickness. They also furnish the middle of the roof of the mouth. 

 The outer nasal processes (also called the lateral frontal processes by 

 His) form on either side a ridge protruding between the eye and the 

 organ of smell, and furnish the material for th- 

 lateral walls of the nose and the ate. Their !.>\\er margin- meet 



