326 



F. L. LANDACRE 



as a structure distinct from the lateral mass, and since the lateral 

 mass contains much material that does not go to form ganglia 

 before undergoing differentiation and has a definite structure 

 and position of its own, it seems better to characterize it as indi- 

 cated above. 



The lateral mass in an early stage in which the neural plate is 

 still nearly flat has the appearance indicated in fig. 1. In Stage 



dor./atma.ss vu. 

 ■pre. au. p/aoode 



D 



Fig. A. A camera tracing of the blastoderm corresponding to fig. 1, showing the 

 broad, flat neural plate. 



Fig. B. A camera tracing corresponding to fig. 3. showing the position of the 

 lateral mass and of the intermediate region. 



Fig. C. A camera tracing four sections anterior to fig. 9, showing the relation 

 of the lateral mass to the neural cord. 



Fig. D. A camera tracing corresponding to fig. 9, showing the relation of the 

 preauditory placode to the dorso-lateral mass. Posterior to this point of a few 

 sections, the auditory vesicle occupies the position of the preauditory placode and 

 dorso-lateral mass. 



II (fig. B), it is separated from the neural keel by a thinner 

 region which I shall designate as the intermediate region to dis- 

 tinguish it from the lateral mass. This thickening extends 

 throughout the whole length of the head and into the cord region. 

 The lateral mass does not become incorporated into the neural 

 cord which forms from the thick central mass, or neural keel, 

 lying between the intermediate regions on either side. 



