, 





VIII. EMBRYOLOGY OF TEREBRATULINA. BY EDWARD S. MORSE. 



YV ITH the great impulse given to the study of Zoology through the labors of Charles 

 Darwin, renewed effort has been made to work up the embryology of those forms which 

 have rendered so little satisfaction from the study of their mature characters, and thus 

 through the labors of European naturalists new light has been thrown upon the develop- 

 mental history of Sagitta, Amphioxus, the Tunicates, and many other aberrant groups. 

 And now while the embryology of nearly every prominent group has been more or less 

 studied, and important relations revealed that would have otherwise been obscured, little 

 or nothing has been done to throw any light on the embryology of the Brachiopods, a 

 class represented by thousands of species in past times, and one of which we have the 

 earliest records in the rocks. 



This dark portion in the history of the Brachiopods seems all the more strange when we 

 recall the many beautiful monographs of various genera of Brachiopods published since 

 Cuvier's famous memoir, in the year 1802, on Lingula, and when it is remembered that a 

 hundred and more species still exist in the seas at present. What little has been accom- 

 plished in this field, however, has shed great light on the natural affinities of the class, and 

 it may be well briefly to recall what has already been done in order to make this portion of 

 their history more complete. 



To Oscar Schmidt is due the credit of giving the first figure of a larval Brachiopod. In 

 the " Zeitschrift fiir ges. Naturwissenschaften," 1854, p. 325, he gives a description of 

 the embryo of some species of Terebratula collected in the North Sea. Accompanying 

 this description a simple figure was given. In this the embryo shows a deep constric- 

 tion in the centre, the free or cephalic portion being wider than the posterior half, which 

 is abruptly truncate at the end, and he infers, and rightly too, that at this end the embryo 

 becomes attached. I add a brief translation of his description. 



The embryos of the Norwegian Terebratula observed by me differ remarkably from the embryo Lingula 

 as described by Owen. They resemble a Euastrum composed of unequal halves; the round end seems to be 

 the anterior. The somewhat narrower hinder portion extends into two projections. In none of the ovaries 

 examined by me for in these were the embryos found had the development gone farther. In the per- 

 fect ignorance in which we now are with regard to the development of Terebratula, every small contribution 

 towards clearing up this question is acceptable. 1 



1 The allusion to the embryo Lingula of Owen has refer- ova. In one egg he suggests the rudiments of a peduncle, 



ence to Prof. Owen's memoir on the Anatomy of Terebratu- The egg, as it escapes from the ovary by dehiscence, often 



Una, forming the introduction to Davidson's British Fossil presents the appearance figured by him, from the thin mem- 



Brachiopoda, published by the Palieontolographical Society, brane still adhering to the egg after its rupture, and conse- 



London. On Plate i. of the Introduction, Owen figures five quent separation, from the cluster. 

 eggs of Linyiila anatitia, which he supposes are impregnated 



MEMOIRS BO6T. SOC. NAT. HIST. VOL. II. 



