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it as representing the latter in its simplest form without any trace 

 of subdivision. This view has very general!)- been adopted. Stieda 

 also recognised the dorsal and ventral groups ot ganglion-cells (of 

 which the former is shown in section in Fig. 46) as belonging to 

 the hinder portion of the brain. Rohde's conception of the brain 

 of .Amphioxus agreed \ery closely with that of Stieda, but he made 

 a more detailed study of its histological character, and defined its 

 limits more precisely. He concludes that the begmning of the 

 spinal cord proper, in the absence of any outward mark of dis- 



Fig. 51. — ^.igiital section through the cerebnil \-esicle ot Amphioxus. i.^fler 



KlTFKEK.I 



.■.:'. C.i%'it^' of cerebr.il wsicle. (■. Kye-spot. ^^'..■. Dorsal group of ganglion- 

 cells (cf. Fig. 46I. rrK Infundibular depression. .".,'. Lobus olfactorius impar. 

 .'.". Tubercuiuni posterius. 



tinction from the brain-region, would lie at the point marked by 

 the appearance of the first of the giant ganglion-cells, wliich he 

 denotes by the letter .\. (Cf Fig. 4S.) 



Quite recently the attempt has been made by Professor vox 

 KuPFFER to determine in detail the delimitation of the cerebral 

 vesicle of Amphio.\us (Fig. 51). The sliglit outpushing of the 

 wall of the vesicle towards the base of the olfactory pit has been 

 mentioned in the text. It was discovered hv L.angerh.ws in 



