mi IM 



alike, become specialised in \.T\ differ 



which there are produce I the \\ell-known layer- di-t in.L'u i-he, 1 hy 

 .M\\ S< m I.T/I:. I -hall n>t -TO ii,t.. f h, . f thi> hi. tological 



ditlerentiation, luit shall iiifiiiioii BOme further points of gen 



importen 



Wiimi.M .Mi i i.i i: in hi- >t.imme-.-nt wieklung des SehorL 

 der NVirhelthiere" ha- clearly -ho\\n. tin- development of 

 originally -inular rj.it ln-lial i-i-ll> of the r-lma tak-- jlac in all 



Vertebrates in two chief directions : a part >t' th<-n: IN m- MI 



cjiith. limn and the specific struct uiv- of the cent ral n"-\ius system 



ganglionic cells and n'r\<'-!i' ire uu-t:iiiiiriilu-'i 



sopfwrting and isoiUtuig elements- im> Mi I.I.I:K'S ra.lial ni.r.- 



the granular [n-ticnlar or molecular] layn>, which i-an be gro 1 

 toLr<'thfr as epithelial .-n-teiitat ive tiiu- (fulcnui :ly, with 



the descendants of the epithelium are 1 conn.-.-! 



elements, which <jrov - from the sunotin<lini: ronnrt-tive ti 

 the epithelial layer for its better nutrition, in the sam<- manner as 

 ill the central ner\ :n. 'I'he-e in-ri-u t hs ar- !! 



artoria n-ntralis ivtiiut- with their extremely thin conincn 

 .-heath-. The Lamprey- alone form an exception, th- 



remaining free from blood-vessela In all other \'rrtlrates 1.;. 



-Is are present, hut they an- limitc'l to the inner 



retina, leaving the outer granular (K..rn.-i-) laser and that of the 

 rnl> and ci.ne> free; the latter have heen dist inirui.-h' 

 t pithelium from the remaining [>oition- with their nerxetihn-- and 

 ganglionic Cells the brain part of the retina. 

 < >t' all the parts of the n-tina tin- 



la.-t to l.e developed. According t the inveetigationfl . 



I'.AI.I . ni\. MAX S< in I.T/I:. and \V. Mi i i .rises as a product 



of the outer ^raliula: which, Colll{X)Sed of line 



spindle -haped element-, i- held to he. a.- ha- 1- utial 



i-y epithelium of th" eye In the ( 'hick t he development of the 

 rod.- and cone- can he made ut on the tenth day of incuh. 

 MAX Sriin.i, eoncernini: \..unir Oatfl and Hal. Lit-, \\liicli 



are l-orn hlind. that the fundament of the rods and cones can be 

 di.-tin.iriti-hed for the tir-t time in the ,-arlv day- after hirth: in 

 other Mammals and in Man. on the contrary, they are foi 

 hefore hirth. 



In all Vertehrates. a- I"!)L: afl i"d- and OOH6i are nt pre-ent, the 

 inner layer of the optic cup is bounded on the -ide toward the outer 

 Liver by an entirely smooth to the memhrana limitan.- 



31 



