136 



of wliicli I give here some pictiiies. In the first figure (Lepidosteiis 

 larva of 5 oM.), the limit between tiie basal primordium (from which 

 the palaeostriatiim arises), and the dorsal (pallia)) primordinm is 

 indicated by a line, the dorsal point of which might even be drawn 

 somewhat more laterally (to coincide with the fiss. endorrhinalis 

 interna). The basal point tie repere of this line lies in the Ussura 

 endorrhinalis externa, only slightly indicated in this stage. 



The paliial part is very small in this stage. 

 In a later stage, the paliial part however in- 

 creases considerably. In fig. 2 and 3 1 have given 

 transsections of a 10 cM. larva and a full grown 

 animal (1.20 M loiigi. These two latter figures 

 repiesent a more frontal level tiiaii figure I, so 

 that the olfactory bnlb is cut, in order to show 

 the reader that here we have really to do with 

 of a a c.M. larva of a paliial part, (p.), which however in these 

 Lepidosteus. fishes does not grow like a real mantle, but 



iV.ö. = basal nucleus merely increases in thickness. The insertion of 

 ornucleuspeduncularis „^^ ^.^^j. „j^.j^hrane is at the place of the A' in 



anterior. . r. ^ , • , , , i n i 



fig. 3, trom which results that nearly ail the 



mantle substance has an intraventricular position. 



h^ig. 1. Transverse 

 section of the forebrain 



Fig. 2. Transverse section of the 

 forebrain of a larva of Lepidosteus 

 (10 C.M.). 



p = pallium. 



lob. olf. 

 ant. 



Fig. 3. Transverse section of 

 the forebrain of an adult Lepidosteus 

 (right half) x = insertion of the 

 roof membrane, p — nervous pal- 

 lium. 



