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given by Kopsch for the trout, we sec that they do not differ so 

 very much, and that the displacement of the hinder end of the 

 embryo is almost the same. In the text of my former paper however 

 I expressed myself rather ambiguously, and broughl my view into 

 a too close contact with that expressed by Oellacher. The figures 

 however show that my scheme differs rather much from that ol 

 Oellachkr. 



But 1 differ from Kopsch in his supposition thai the head-end 

 of the developing embryo is a fixed point on the periphery of the 

 egg. I find myself here quite in harmony with Sumner, who draws 

 from the large series of his extremely careful and exact experiments 

 the conclusion, that "the head end also grows, or at least moves, 

 forward, though to a much smaller extent" (1. c. page 115), and 

 says : "1 regard it as highly probable (see Exp. 1, 3, 34, 35, 36 

 and Fig. 32) that the primary head end grows - - or is pushed - 

 forward from an original position oil the margin" (1. c. page 139). 



From different experiments of the author we may draw the 

 conclusion, that in many cases this forward growth of the head-end 

 is rather extensive (exp. No. 6, 10, 11 (partly), 26, 35, tig. 10), and 

 experiment N u . 6 (table VI11) among others shows, that under circum- 

 stances the direction of growth may be entirely reversed, so that 

 the tail-knob of the embryo remains at the same place, and the 

 head-end bends round the surface of the yolk. 



Kopsch too, in his paper : "Ueber die morphologische Bedeutung 

 des Keimhautrandes und die Embryobildung bei der Forelle", describes 

 an experiment with simular results in the trout. 



So it is not unreasonable to suppose, that in the spherical egg of 

 the Muraenoids during the covering of the yolk the head end of 

 the embryo is moving forward, and to a certain extent follows the 

 growing blastodermring, which is the case chiefly during the later 

 stages of the covering of the yolkmass, as I showed in my scheme. 

 During the first stages of development it is chiefly the tail-end of 

 the embryo which travels backwards, (see the scheme in my former 

 paper and fig. 1 — 3 or plate 2), and Kopsch is right to locate here 

 the centre of growth of the embryo. 



The conclusion of Sumner, that for some time prior to the closure 

 of the blastopore, the ventral lip of the latter (former anterior 

 margin of the blastoderm) travels much faster than the dorsal lip 

 (1. e. p. 115) is quite in harmony with my results for (he murae- 

 noid egg described in my former paper. *) 



] ) Petrus Camper, 1. c. p. 196. 



