HEREDITY. 



407 



eleventh air space or chamber being open and without 



divisions would then appear to be the living chamber 

 which the animal occupied when it built the tenth sep- 



Fig. 116. 



turn. Normally the shell really continued to progress 

 from the tenth septum by additions to the outer wall 

 and put in new septa behind it, together with the con- 



Fig. 117. 



necting tube until it reached s , and finally the las*- 

 septum, Is. This one, Is, was really the last one built 



rocky matrix in which the shells occur and is often, as in this specimen, al- 

 lowed to remain. See also 4, 5, 6, of Fig. 119, which show the comma shaped 

 umbilical perforations or openings left at the center through the crytoceran 

 form of the young. 



