326 ARTHUR WILLET. 



as a modified gill-slit, but thinks that its antimere is the larval 

 mouth which he calls the Tremostoma. This he homologises 

 with the left spiracle of Selachians. The Tunicate mouth is 

 for him represented in Amphioxus by the pre-oral pit^ which 

 he calls the Antostoma. 



For the rest, van Wijhe records some most important obser- 

 vations on the peripheral nervous system and on the muscula- 

 ture of Amphioxus. 



5. W. Salensky ('' Morphologische Studien anTunicaten: 

 I, Ueber das Nervensystem der Larven u. Embryonen von 

 Distaplia magnilarva," ' Morph. Jahrb./ xx, pp. 48 — 74) 

 appears to come to similar results to those already published 

 by Hjort with regard to the neuro-hypophysial system of 

 Distaplia. He also comes to a conclusion on which I have 

 dwelt in the foregoing pages in connection with Ascidia men- 

 tula. Salensky finds likewise in Distaplia '^ dass alle Theile 

 der Sinnesblase : Retina, Linse, Pigmentschicht und Otoli- 

 thenzelle durch die Difi'erenzirung einer und derselben Epi- 

 thelschicht der primitiven Gehirnblase enstehen." 



6. W. K. Brooks (" Salpa in its Relation to the Evolution 

 of Life/' ' Studies from the Biological Laboratory, Johns 

 Hopkins University/ vol. v, No. 3, Baltimore, 1893). 



At the conclusion of this otherwise interesting memoir. Prof. 

 Brooks devotes several paragraphs (pp. 199 — 201) to a criticism 

 of my " Studies on the Protochordata " (No. I, ' Quart. Journ. 

 Micr. Sci./ vol. xxxiv, Jan., 1893). 



In the body of his memoir. Professor Brooks develops, with 

 great elaboration, the view that "the chordata type was 

 evolved under purely pelagic influences," and that Appendi- 

 cularia is the direct descendant and somewhat modified living 

 representative of this pelagic archetype. 



Then, referring to my work, he says (p. 199), " While the 

 author seems to agree with me in rejecting Dohrn's view that 

 the Tunicates are degenerated fishes, he holds that the Ascidians 

 exhibit, during their development, certain features of resem- 

 blance to other primitive chordata which are not exhibited by 

 Appendicularia ; and he believes that these characteristics prove 



