1898] NOTES AND COMMENTS 375 



record of all deaths which came to his knowledge, and he finds it 

 average 8 to 10 a year. As he points out, Washington has estab- 

 lished a colony of beavers in the Xational Park, and it is a complete 

 success. The animals are kept to a woody valley through which 

 runs a small water-course, and they there construct their clams and 

 tunnels, quite familiarised to the occasioned presence of man, who 

 can watch their daily life and works unheeded. He hopes that 

 France will similarly protect the few last beavers remaining in the 

 Camargue delta, and we cordially echo his sentiments. 



A. T. MASTEBMAJN ' ON THE DlPLOCHORDA ' 



Some preliminary notes by Mr Masterman in the Proceedings of 

 the Royal Society of Edinburgh, for 1896, and also in the Zoologischer 

 Anzeiger, paved the way for a more detailed paper of great interest 

 in the Quarterly Journal for Microscopical Science (vol. xl., 1898). 



The paper is divided into two parts — (1) on the structure of 

 Actinotroclia, and (2) on that of Cephalodiscus. As the result of an 

 exhaustive study of Actinotroclia (the curious larval form of Phoronis) 

 by means of sections, Mr Masterman comes to the conclusion that 

 the close similarity in structure to the three members of the group 

 now commonly called Hemichorda points to a genetic connection, but 

 that Phoronis and Cephalodiscus should be considered as constituting 

 a distinct sub-division of the Chordata, for which the name of Diplo- 

 chorda is proposed, owing to the possession by its members of paired 

 lateral notochords. Balanoglossus is supposed to represent a later 

 phylogenetic stage, in which these lateral notochords have fused in the 

 median line. As there are certain animals which have always been 

 objects of disagreement on account of their generalized types and the 

 doubtful nature of their genetic relationships, so, too, there have 

 always been certain organs or structures around which controversy 

 has continually raged ; the notochord is one of these, as students 

 of the literature of Balanoglossus are well aware. If Mr Masterman's 

 views are correct, and the paired structures he describes both in 

 Actinotroclia and in Cephalodiscus are really of notochordal value, he 

 has established a fact of the greatest scientific interest and phylo- 

 genetic importance, and we cannot but think he has made out a very 

 good case for the homology. The figures on plates 25 and 26 are, we 

 think, especially instructive, but they are nevertheless not universally 

 regarded as convincing. Mr S. F. Harmer, whose views on the noto- 

 chord of Cephalodiscus have been expressed in the Zo.oh>gisc]icr Anzeiger 

 (vol. xx., p. 342), while fully agreeing with Mr Masterman as to the 

 relation of Plioronis with Balanoglossus, does not admit the homologies 

 with Cephalodiscus, on which the main argument depends. Mr 

 Masterman claims to show that the structure described by Mr Harmer 

 as the notochord in Cephalodiscus is really the subneural gland, and 



