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DESCRIPTION OF FIGURES. 



Abbreviations. 



ch. — chiasma. hb. — habena. 



J. d. — dorsal sack. hy. — hypophysis. 



d. I. — lateral diverticula. nitp. — metaplexus. 



^/z.— epiphysis (epiphysis II.) par. — paraphysis, 



epi, I. — cephalic epiphysial vesicle vel. — velum transversum. 



(epiphysis I.) //. — optic nerve. 



Fig. I. Transection of the Brain of Aviia at the level of the cephalic 

 epiphysial vesicle, showing its fiber connection with the left habena, and the 

 lateral diverticula. The cephalic tips of the optic lobes and the connective 

 tissue adjoining, which occupy space enclosed by the outer line are omitted 

 to simplify the figure. 



Fig. 2. Transection of the prosencephal of Lepidosteus, to show the epiphy- 

 sis (11), dorsal sack, paraphysis, and the lateral diverticula of the cavity. 



Fig. 3. Transection through the prosencephal of Aniia, showing the 

 epiphysis, dorsal sack, paraphysis and cephalic extensions of the diverticula. 



Fig. 4. Transection of the brain of Atnia, showing the same general fea- 

 tures as figure 3, but farther caudad, at the level of the opening of the para- 

 physis. 



P^S- £• Transection of the metencephal of Lepidosteus, showing the lateral 

 extension of the cavity beneath the metaplexus. 



