THE LENS-PROBLEM. 235 



mic anadidymus component could not be accounted for by 

 "hereditary reminiscences," while chance contact of remnants 

 of dissociated ophthalmoblastic material of both sides with the 

 epidermis does account for the origin of both lenses as well as for 

 their asymmetrical position. Neither of them has arisen from 

 predetermined, lens-forming cells "durch Erinnerung," but from 

 indifferent ectoderm in response to stimuli from remnants of 

 potential optic cups on the epidermis. 



The other "independent" lenses and lentoids described by 

 Mencl ( '08) can even much easier be demonstrated to be due to 

 the same origin blastolysis and subsequent contact of fragments 

 of optic cup substance with the ectoderm. From his description 

 of sections of the embryos underlying the Figs. 4, 5, 6, 7 and 8 the 

 reader will easily gather that in these cases fragments of optic- 

 cup substance 1 have been profusely dispersed and in places of 

 contact with ectoderm gave rise to lenses or lentoids. Mencl 

 did not appreciate the full significance of his own observations, 

 for referring to such an optic fragment ("Pigmentanhaufung," 

 Fig. ^X, he says: "Was dies Gebilde bedeutet, kann ich nicht 

 entscheiden das Vorhandensein des Pigments jedoch, sowie die 

 retinaartige Anordnimg der Zellen in der benachbarten Hirnwand 2 

 lasst die Meinung entstehen, dass es sich dabei um irgend ein 

 Rudiment einer atypisch und selbststandig zur Entwicklung 

 gelangten Augenkomponente handelt" (p. 447). It is, indeed, 

 difficult to understand just why, in spite of these observa- 

 tions, Mencl claims that in these embryos "die selbststandige 

 Entwicklung der Linsen iiber jeden Zweifel erhaben ist" (p. 



447)- 



1 have recently examined sections of a number of deformed 



Salmonid embryos (of another species) with such "independent" 

 lenses. The publication of the observations made on this ma- 

 terial being reserved for a future publication, it may suffice to 

 state that the conditions noted in several of these embryos bore 

 a very striking resemblance to those in the embryos lately de- 

 scribed by Mencl ('08). Here, too, subjective interpretation 



1 "Pigmentanhaufung," "Pigmentblaschen," " Pigmentfleck," "eine homogene, 

 schwarze, langliche Pigmentmasse, welche in die Falte der retina-artigen Hirmvand 

 hineinragt" (Mencl '08, p. 447). 



2 My own italics. 



