ZOOLOGY. 285 



a long period were regarded as Mollusks. These diverse 

 tendencies have been both exemplified during the past year. 

 On the one hand, like Semper, Mr. Hoppe-Seyler urges the 

 separation of Branchiostoma from the Vertebrates, and ex- 

 presses surprise that systematic zoologists should have so 

 readily associated the type with the members of that branch ; 

 he contends that the Cephalopods are even nearer the Ver- 

 tebrates than is Branchiostoma r , and affirms that the form 

 in question has nothing in common with the Vertebrates but 

 the chorda dorsalis and the development of the venous sys- 

 tem above it and the alimentary canal below : " It differs," 

 he says, "from the Vertebrates in having no brain, no closed 

 vascular system with red blood-corpuscles, no bile-secreting 

 liver, and no gelatin-yielding tissue." In consideration of 

 these deviations and the facts in the development and com- 

 position of the tissues of animals generally, he arrives at the 

 conclusions noted adverse to the association of Branchiosto- 

 ma with the Vertebrates. On the other hand, Professor E. 

 Ray Lankester, of Oxford, in "Notes on the Embryology 

 and Classification of the Animal Kingdom," published in the 

 Quarterly Journal of Microscopical Science for October, 1877 

 (vol. xvii., p. 399-454), has claimed not only Branchiostoma, 

 but also the Tunicates, to be representatives of the Verte- 

 brate branch or "phylum," as he prefers to call it; and 

 forms for the Tunicates, under this phylum, a "branch" 

 named ZTrochorda, co-ordinate with two other branches 

 Cephalochorda, represented by Amphioxus, and Craniata, 

 constituted by all the remaining Vertebrates. He thinks, 

 like Dr. Anton Dohrn, that evolution may tend in different 

 directions, and that, although on the whole it is in the direc- 

 tion of progression from the low to the high, it may be, and 

 in a number of cases he believes actually has been, towards 

 degradation. " So strong," says he, " is the case in favor of 

 degeneration, that at present all that can be said against it 

 and in favor of progression, with regard to any particular 

 case, is this that the general doctrine of evolution justifies 

 us in assuming, at some period or other, a progression from 

 the simplest to the most complicated grades of structure ; 

 that we are warranted in assuming at least one progressive 

 series leading from the monoplast to man ; and that until v:e 

 have special reason to take a different view of any particular 



