274 HOVEY JORDAN 



solution of these questions, seemingly, must await further studies 

 from this point of view upon the development, structure and function 

 of the photoreceptive elements both in the skin and cord. Among such 

 problems the questions of the development of the direction eyes of 

 Amphioxus, and a search for conditions intermediate between them 

 and the typical retinal elements of the lateral eyes, as well as a phylo- 

 genetic study of cutaneous photosensitivity, are clearly demanded. 



BIBLIOGRAPHY 



BALFOUR, F. M. '81 A treatise on comparative embryology, London, ii, 655. 

 BLAATJW, A. H. '09 Die Perzeption des Lichtes, Recueil des Travaux botaniques 



Neerlandais, v, 209, pi. 23, 24. 

 BOVEKI, T. '04 Zool. Jahrb., Suppl. vii, 409. 

 CARLTON, F. C. '03 Proc. Amer. Acad. Arts and Sci., xxxix, 259. 

 CROZIER, W. J. '17 Anat. Rec., xi, 520. 

 DUBOIS, R. '90 Compt. rend. Acad. Sci., Paris, ex, 358. 

 EIGENMANN, C. H. '00 Biological lectures. Mar. Biol. Lab., Woods Hole, 



1899, 113. 

 FROSCHEL, P. '08 Sitzungsb. d. k. Akad. d. Wissensch., Wien, cxvii, Abt. 1, 



235. 

 GRABER, V. '84 Grundlinien zur Erforschung des Helligkeits- und Farbensinnes 



der Tiere, Prague u. Leipzig, viii, 322. 

 JORDAN, H. '17 This Journal, xliii, 438. 

 KORJ&.NYI, A. '92 Centralbl. f. Physiol., vi, 6. 

 LANKESTER, E R. '80 Degeneration, London, 75. 

 LOEB, J. '11 Winterstein's Handb. d. vergleich. Physiol., iv, 451. 

 PARKER, G. H. '03 This Journal, x, 28. 



'05 This Journal, xiv, 413. 



'08 Amer. Nat., xlii, 601. 



'09 This Journal, xxv, 77. 



PARKER, G. H., AND PATTEN, B. M. '12 This Journal, xxxi, 22. 

 PAYNE, F. '07 Biol. Bull., xiii, 317. 



