1893. OWEN. 25 



Twenty-one years later Professor Owen published an elaborate and 

 well-illustrated memoir on that interesting, abnormal, but mis-named 

 arthropod, the King-Crab {Limulus polyphcemiis), which is no crab, and 

 has since been definitely promoted out of the class of water- 

 breathing Crustacea into that of the air-breathing Arachnida and 

 associated with the Spiders and Scorpions." He detailed the mus- 

 cular, nervous, digestive, and generative systems, and proposed the 

 term " Cephaletron " for the anterior division of the body, and 

 "Thorocetron " for the second ; while he declared "the chief fossorial 

 agent, as indicated by the size and disposition of the principal mus- 

 cular masses, to be the cephaletral digging-shield." While recognising 

 some of the Arachnid affinities of the King-Crab as then maintained 

 by Strauss-Durckeim and Latreille, Owen did not admit the necessity 

 for removing the genus from the order of Merostomatous Crustaceans. 

 Professor Owen's numerous memoirs on the anatomy of the 

 Brachiopoda were second only in importance to his researches on the 

 Cephalopoda. In both classes he founded orders which have been 

 generally'- accepted by biologists, and still maintain their position as 

 recognised additions to zoological nomenclature and classification. 

 In the article on " Mollusca," published in the eighth edition of the 

 " Encyclopedia Britannica," the sub-kingdom Mollusca was divided 

 into the Heterogangliata, with one nerve ganglion, and the superior 

 Hoviogangliata of Owen. The group was compared to a tree, with 

 the Cephalopoda at the summit, one of the roots appeared to be lost 

 in the Turbellarian and the Trematode families of Abranchiate 

 Vermes ; the Brachiopoda conducted to the Bryozoa, and both, with 

 the Tunicata, were considered as " mollusc-like " rather than 

 molluscan. The Brachiopoda were regarded as a class equivalent in 

 value to the Lamellibranchiata, and were placed between those 

 acephalous molluscs and the sea-squirts, that is to say, between the 

 " Acephales testacees," and the " Acephales sans coquilles " of 

 Cuvier. In 1833 the anatomy of the " Cuvierian genera of Brachio- 

 poda," more especially of Terehratella and Ovhicula (now known as 

 Discina), were described. The circulatory, muscular, and nervous 

 systems of other genera were more fully investigated twenty years 

 later, and the results published, accompanied by beautiful drawings 

 by the author, in a " Memoir on the Anatomy of Terebratula," in the 

 Introduction to Davidson's classical Monograph of the " British 

 Fossil Brachiopoda,'" elucidating some points in the structure of 

 W aldheimia and Lingula. Owen's brachiopodal hearts are now known 



1^ " Limulus an Arachnid," by E. Ray Lankester, F.R.S. Quart. Journ. Micros. 

 Sci., 188 1. 



^2 Waagen and F. A. Bather excepted. Mr. A. H . Foord, in his exhaustive ' ' Cata- 

 logue of the Fossil Cephalopoda in the British Museum," 1888 (p. viii., Int., part i.. 

 Order Nautiloidea), states that " no evidence has as yet been brought forward that 

 the fossil forms included by Owen in the Tetrabranchiata were other than four- 

 gilled." 



