314 JOHN WARREN 



on various forms of lizards, Lacerta muralis, agilis and viridis, and 

 also on the turtle, Chrysemys marginata. The other papers were 

 the following: 1. C. S. Minot. The Morphology of the Pineal 

 Region based on its Development in Acanthias, 1901. 2. F. 

 Dexter. The Development of the Paraphysis in the Common 

 Fowl, 1902. 3. J.Warren. The Development of the Paraphysis 

 and Pineal Region in Necturus maculatus, 1905. 4. R. J. Terry. 

 The Morphology of the Pineal Region in Teleosts, 1910. As a 

 great deal has been written on the details of this region, especially 

 in the lacertilia, it seemed desirable to consider the growth of 

 the structures arising from this part of the brain rather from the 

 standpoint of topographical development, and with this end in 

 view wax reconstructions of the fore and mid brain of each stage 

 have been made. Owing to the amount of material available in 

 the Harvard Embryological Collection, a more complete series 

 of stages of the complicated development of this region can be 

 shown than has been described heretofore. The reconstructions 

 display the structure of this region better than ordinary sections 

 and also demonstrate more clearly the topography of this part of 

 the brain. 



DESCRIPTION 



Lacertilia 



The observations were made on specimens of Lacerta muralis 

 agihs, and viridis. The models are magnified 110 diameters. 



Fig. 1 is a model of a part of the brain of an embiyo of Lacerta 

 muralis of 1.8 mm. A gi'oove marks the limit between the pros- 

 encephalon, P., and the mesencephalon, M. The stalk of the 

 optic vesicle appears on the lateral aspect of the prosencephalon 

 and there is as yet no sign of any further subdivision of the fore 

 brain. 



Fig. 2 is a model of the left half of the brain of Lacerta muralis 

 of 2 mm. Here a slight angle, V, is seen in the roof of the fore 

 brain which is the anlage of the velum and marks the sub-divi- 

 sion of the fore brain into telencephalon, T, and diencephalon, 

 /. D and II. D. There is a sHght ridge passing downward from the 



