Report of the State Urologist. 



541 



Post embryonic Staoi s. 



With the completion of the protegulum and the incipient 

 development <>l* the lophophore, the embryonic condition of 

 brachiopod may be regarded as closed. The subsequent periods 

 in the life of the animal may be divided into (a) the infantile ; 

 (b) the adolescenl ; (o) the adult ; (d) the senile. 



During the infantile condition, additions made to the profo 

 lum usually modified the outline of the shell, and hear only 

 the concentric lines upon the surface. The caecal perforations of 

 the shell appear at this period (Tkrebrait- 

 lina). The animal is usually attached by 

 its pedicle, but in Gtlottidia this organ is 

 not yet protruded from between the valves. 

 In the adolescent period the shell takes 

 on the normal outline of the species, and 

 surface plications and other external orna- 

 ment and configuration now make their 

 appearance. The lobes of the lophophore 

 become developed, the digestive tract 

 extended and completed, and, in Glot- 

 tidia, the pedicle is protruded and highly 

 developed. After passing the period of 

 maturity, the senile shell undergoes vari- 

 ous changes. Callosities and deposits of 

 adventitious calcareous matter are formed 

 about the internal processes; the valves' 

 are thickened instead of being increased 

 in diameter, the characteristic ornamenta- 

 tion of the shell may be temporarily or per-/ 

 manently lost, and the surface become 

 smooth. Growth in this period of decline 

 is reversional, manifesting a resumption of FlG - '^--TerebratuUna. a very 



. ° ' young shell, with pedicle, cilia, 



infantile characters. Hyatt has defined setee and punctee developed, 

 two stages of senile growth ; one prelimi- (x300) (MoRS£ )- 

 nary or progressional, that in which the characters of maturity 

 are disappearing in the reverse order of their appearance ; the 

 other, extreme or final, when the shell lias finally reverted to 

 its own condition during the infantile period. 



A chapter on Classification will follow the discussions of the 

 genera. 



93 



