10 THE VOYAGE OF H.M.S. CHALLENGER. 



and its development was, in tlie main, correct, i.e., the apophysis of Waldheimia is at 

 an early stage fastened in a threefold manner ; firstly, the lameUee are connected to the 

 hinge-plate by the crura ; secondly, the lamellae are connected with a septum ; and, 

 finally, the reflected part of the loop is connected with the lamellse and the septum by 

 two vertical walls placed close together ; as the shell is enlarged the loop expands in 

 breadth, the united lamellee split from below backward, dissolve connection with the 

 septum, and the lateral walls vanish. In this representation, no correction is to be made ; 

 but, besides being now enabled to proceed one step further into the development, I can 

 also replace my earlier simple drawings by better and more complete illustrations." 

 Herr Friele then proceeds to describe in detail each modification assumed by the loop 

 from its complicated condition up to its simple adult form in which it is attached only 

 by its crura to the hinge-plate. He adds : " The history of the development of the 

 Brachiopoda has until recently been very little known, and it was not tUl 1871 and 

 1873 that Prof. Morse published a complete description of that of Terehratulina 

 septentrionalis, Couth.'' By comparing the manner in which the formation of the 

 apophysary system takes place in the latter, with the above described in Waldheimia, 

 an essential difierence is observed. Terehratulina proceeds with deviation direct towards 

 the form that characterises the genus ; Waldheimia, on the contrary, forms first a very com- 

 plicated loop, and passes then to a more simple construction. 



In the Proceedings of the Zoological Society for 1878, Dr Gwyn Jeffreys corroborates 

 the observations of H. Friele, and I have likewise perceived from the Challenger 

 material that a similar development of the loop, as that observed in Wold, cranium and 

 W. septigera, takes place in Wald. herguelenensis and W. Jlavescens, and that this is pro- 

 bably the rule in every species of the genus. A similar modification of the loop takes 

 place in Wald. lenticidaris, a species nearly related to Wald. herguelenensis. 



I also question very much whether Magasella, Dall, is a good genus or even sub- 

 genus. From the study of a series of the so-termed Magasella evansi, 1 am convinced 

 that this last is only the young stage of Terehratella cruenta, and it is probable that in the 

 young of Terehratella the septum was comparatively much larger and more elevated than 

 it became afterwards in the adult form. These important questions and investigations, 

 relative to the development of the loop in different genera, are, as it were, a new study, 

 which, when properly followed up, will eventually lead to the most imjDortant results. 

 It will now, therefore, be very desirable to obtain and examine large series of specimens 

 of the same species, at different stages of growth (as has been done by H. Friele for 

 W. cranium and W. septigera), a study that will repay those naturalists who may be able 

 to procure the necessary material. 



' Early Stages of TerelratttUna septentrio)ialis, &c., Mem. of the Boston Soc. of Nat. Hist., vol. ii. parts 1 and 3. 



