Ill 



STUDIES IN THE DEVELOPMENT OF 

 THE BRACHIOPODA* 



1. DEVELOPMENT OF THE BRACHIOPODA 

 Paet I. Introduction t 



(Plate XI) 



The Brachiopoda have been so carefully studied that any- 

 new general conclusions regarding them must be naturally 

 based upon features not heretofore considered. In other 

 classes of animals such important results have been recently 

 reached by the application of the law of morphogenesis as 

 defined by Hyatt, that the writer was led to study the 

 Brachiopoda from this standpoint. The facts observed by 

 this method are mainly new to the class, and considerably 

 affect the taxonomic positions and affinities of the various 

 families and genera. 



The value of the starres of growth and decline in work 

 relating to phylogeny and classification is now generally 

 admitted. The memoirs of Hyatt, Jackson, and others 

 amply show that the clearest and simplest understanding of 

 a group may be thus reached. The application of the prin- 

 ciples of growth, acceleration of development, and mechan- 



* No revision of these papers has been undertaken further than to bring the 

 nomenclature of genera and sj)ecies up to date ; also the current terms of 

 anxology, as agreed upon by Hyatt, Buckman, and Bather, have been substituted 

 for those first proposed. 



t Amer. Jour. Sci. (3), XLI, 343-357, pi. xvii, 1891. 



