History of a transient nervous apparatus in certain Ichthyopsida. 



417 



Explanation of Plates. 



List of reference letters. 



C. C capsule cells, 



ct cartilage, 

 d. c degenerating cell, 

 ep epiblast, 

 9 gut, 

 gl.C transient ganglion-cell, 

 gl, c. c centrally lying transient 

 ganglion-cell, 

 l.l lateral line, 

 I. n lateralis nerve, 

 mp myotome, 

 n notochord, 



n,p nerve-process of a ganglion- 

 cell, 

 s. d segmental duct, 

 s. n sub-epiblastic transient 

 nerve, 

 sp. C spinning ganglion-cell, 

 tn transient nerve, 

 V vacuole in a degenerating 

 ganglion-cell, 

 W. gl. C wandering transient gan- 

 glion-cell. 



Unless otherwise described, all the figures relate to Raja hatis. 



aid of an Abbe camera. The 

 approximate magnifications are 



Zeiss A, 

 Zeiss D, 

 Zeiss F, 



Hartnack 5, oc. 2 = 140. 

 compensât, oc. 4 == 230. 

 4 = 525. 



All the figures were drawn with the 

 following lenses were used, and their 

 given below. 



ocular 2 == 50 diameters ; 

 oc. 2 = 225; Zeiss D, 

 oc. 2 = 500; Zeiss F, compensât, oc. 



Seibert 4 mm apochromatic, oc. 2 = 225. 



Leitz 2 mm pantachromatic, oc. 2 = 500. 



The figures on Plates 22, 23, 24, 25 have been reduced by the 

 lithographer to two-thirds of their former size. This is indicated in 

 the description by such figures as 225 X f- Except where otherwise 

 stated, the figures are portions of transverse sections. 



Plate 22. 



Pig. 1. Shows the dorsal portion of the spinal cord, where certain 

 of the cells have taken on ganglionic characters. To the left of the 

 figure are two such, which have spun out processes towards the muscle 

 plate. The cells of the future spinal ganglion are still migrating from 

 the lips of the cord. Embryo No. 155. About 9,5 mm, 100 somites. 

 Magnif. 500 X I- 



