II. Ox THE EARLY STAGES OF TEREBRATULINA SEPTENTRIONALIS (Couthouy.) 



By EDWARD S. MORSE. 



Read October 20th, 1869. 



JL HERE is hardly a group among the lower animals (if we consider the relatively small 

 number of species represented by it) that has attracted the attention of so many natural- 

 ists as the Brachiopoda. The names of Cuvier, Owen, Vogt, Huxley, Hancock, Gratiolet, 

 Lacaze-Duthiers, Bouchard-Chantereaux, Miiller, Davidson, Carpenter, King, d'Orbigny 

 and a host of others, are sufficient evidence of the interest felt in a group whose organ- 

 ization links them so closely with the past. 



The desire to interpret through a knowledge of its living forms the many species which 

 are now extinct, as well as to ascertain the relations it bears to the other divisions of the 

 animal kingdom ; the contemplation of a group whose maximum development in genera 

 and species was attained in the Devonian age, though its representatives are strewn 

 through the rocks of all ages since the dawn of life upon the globe ; the remarkable fact 

 that among the earliest forms of organic life known, are genera whose species can hardly 

 be distinguished from present existing forms, all explain the attractions its study has 

 afforded alike to Zoologists and Paleontologists. 



The splendid memoirs upon the Brachiopoda by some of the authors just mentioned, 

 more particularly those of Albany Hancock, 1 Vogt and Gratiolet, offer but little 

 encouragement to one entering the field with the expectation of gleaning anything new. 

 While, however, the anatomy and histology of the adult animal of several species has 

 been carefully worked up, little or nothing has been done toward elucidating the embryol- 

 ogy, or the early stages of the class. Fritz Miiller 2 has given in a short note a descrip- 

 tion and two figures of what he considers an early stage of a species of Distinct, and 

 Lacaze-Duthiers 3 has made some extremely interesting observations on the embryo of 

 Thecidium. Aside from these two papers, we know of nothing whatsoever relating either 

 to the embryology or the early stages of the Brachiopoda. The importance and neces- 

 sity of some information regarding the embryology of these animals has been urged by 

 many writers, for it was believed that the relations between them and the Polyzoa, as 

 urged by Agassiz, Milne Edwards, Huxley, Hancock, Dana and others, would be verified, 

 when the development of Brachiopoda was known. In this path of inquiry the investi- 

 gator will find an open field. 



For a long time I have been interested in the relations of the class under consideration, 



1 On the organization of the Brachiopoda. Philosophical 2 Archiv fur Anatomie Reichart et Du Bois Raymond, 



Transactions of the Royal Society, London, 1858, vol. 1860, p. 72. 



CXLVIII, part 2. Histoire de la Thecidie. Annales des Sciences Nat. 4th 



series, tome XV, p. 262. 



JJKMOIHR HOST. SOC. NAT. H1RT. VOL. II. 8 



399367 



