176 INTERNAL FACTORS IV. i 



There was, however, no operculum. The anterior end was 

 occupied -by a mass of mesenchyme. There was no sign of a 

 regeneration of .any of the lost organs except the anterior end 

 of the notochord. The nerve ganglia were normal, but the spinal 

 cord underwent degeneration. In spite of this the creatures 

 could execute spontaneous and reflex movements. 



What this experiment shows is, of course, that the organs of 

 the trunk are not dependent for their development upon the 

 presence of the brain; fresh researches would be necessary to 

 determine how far in each case the parts are self-differentiating. 

 In the second place the brain and eyes, when removed at this 

 stage, cannot be remade by the tissues, but remain behind. So 

 far, therefore, the body is at this stage an inequipotential system, 

 as Driesch would call it. "We know, however, that at an earlier 

 stage the parts of the body are equipotential. We have, in fact, 

 only another instance of that loss of totipotentiality, of that in- 

 crease of independence and self -differentiation which takes place 

 as development proceeds. Here, however, we are anticipating 

 a conclusion which can only be completely stated after a discus- 

 sion of the experiments performed on eggs of other types. 



LITERATURE 



H. ENDRES and H. E. WALTER. Anstichversuche an Eiern von Rana 

 fusca, Ier und II ter Teil, Arch. Ent. Mech. ii, 1896. 



A. C. EYCLESHYMEB. Bilateral symmetry in the egg of Necturus, 

 Anat. Am. xxv, 1904. 



A. HERLITZKA. Contributo allo studio della capacita evolutiva dei 

 due primi blastomeri nelF uovo di tritone (Triton cristatits), Arch. Ent. 

 Mech. ii, 1896. 



A. HERLITZKA. Sullo sviluppo di embrioni completi da blastomeri 

 isolati di uova di tritone, Arch. Ent. Mech. iv, 1897. 



0. HERTWIG. Ueber den Werth der ersten Furchungszellen fur die 

 Organbildung des Embryo, Arch. mikr. Anat. xlii, 1893. 



F. KOPSCH. Ueber das Verhaltniss der embryonalen Axen zu den 

 drei ersten Furchungsebenen beim Frosch, Intemat. Monatschr. Anat. 

 u. Phys. xvii, 1900. 



T. H. MORGAN. Half-embryos and whole-embryos from one of the 

 first two blastomeres of the Frog's egg, Anat. Anz. x, 1895. 



T. H. MORGAN and E. TORELLE. The relation between normal and 

 abnormal development (iv) as determined by Roux's experiment of 

 injuring the first-formed blastomeres of the Frog's egg, Arch. Ent. Mech. 

 xviii, 1904. 



