CHONDEOCRANIUM OF THE LARVAL HERRING. 



1217 



5, The Chondrocranium. 



a. Tlie 5 mm. Stage. 



This description is based on the study of transverse sections of 

 a specimen nearly 5*5 mm. long. Sections, for confirmation and 

 comparison, of slightly longer specimens were also cut (text- 



fig- 2)- ... 



In front, the chondrocranium is a thin plate of cartilage, in the 



form of a deep, nearly straight-sided trough, about half as deep 

 Text-figure 2. 



s5^v5V77/7; 



/^&mi7! 



Lateral views of early stages of Larval Herring. X 120. From reconstructions. 



as it is broad. A little further back the sides turn up, and 

 separate from the median part forming large upturned pro- 

 cesses, which lie on each side between the brain and the eyes. 

 The median part becomes a somewhat narrower nearly flat plate, 

 which soon divides into two narrow processes enclosing a large 

 foramen in which the pituitary lies. These enclosing processes 

 are the TrabecuJas Cranii. 



