turner: reconstruction of lizard brain. 113 



lobe separated from the optic thalami by a shallow constriction. 

 The hypophysis is situated directly beneath the infundib- 

 ulum, and in this stage its diameter is about half of that of the 

 infundibulum. The pineal apparatus (H) is attached to the 

 optic thalami between the lobes of the cerebrum and extends 

 backward and upward from the point of attachment, lying at 

 an angle of about thirty degrees from the horizontal plane. 

 The parietal eye lies just above the posterior end of the pineal 

 body. 



The optic lobes (D) lie at an angle of about thirty-five de- 

 grees from the horizontal and are connected anteriorly to the 

 optic thalami and ventrally and anteriorly to the medulla. A 

 shallow vertical groove traverses the optic thalami at its pos- 

 terior end and roughly separates it from the optic lobes. 



The cerebellum (E) is relatively very small. It occurs as 

 a median lobe at the base of the optic lobes with its long axis 

 approximately parallel to the axis of the optic lobes. 



The medulla (F) occurs directly under the division between 

 the optic thalami and the optic lobes. It extends forward for 

 a short distance, and then turning sharply backward it makes 

 a U-shaped loop. The ventral horn of the loop unites poste- 

 riorly with the spinal cord (G), which bends sharply down- 

 ward. Between the horns of the loop is the forward extension 

 of the cerebellum. 



cavities of the brain. 



The cavities of the olfactory lobes (olfactory ventricles) ap- 

 pear as mere slits which twist spirally through an angle of 

 nearly 180 degrees between their anterior end and the ol- 

 factory peduncle. 



The cavities within the peduncles themselves are represented 

 by mere lines, the walls lying in apposition. 



The cavities of the cerebral lobes (first and second ven- 

 tricles) are also represented for the most part as curved slits, 

 there being very little actual free space between the walls. 

 Fig. 7 shows the real nature of the cavities, while fig. 9 

 shows their vertical and fig. 8 their horizontal limits. The 

 cerebral cavities connect with the cavity of the optic thalami 

 through paired openings called the foramen of Monro. The 

 opening is surrounded and partially filled by a plexus of 

 slender, fingerlike processes. 



The third ventricle is a thin vertical slit in the middle of 

 the optic thalami. (Fig. 6, 3V.) It extends ventrally into the 



