430 8. Abstammungslehre. 



the Law of Recapitulation with regard both to the nervous systera and other 

 organs, e. g. the origin of cartilage, the position of the infundibulum (the ori- 

 ginal mouth), the nose, gills, thyroid etc. Finally he points out that modern 

 research has largely destroyed the Germ-layer theory, so that no valid objection 

 can be brought against bis hypothesis on this ground. 



Prof. E. W. Mac Bride criticised Gaskell's hypothesis, on the grounds 



1. that no precedent exists for the formation of a new alimentary canal; 



2. the ciliation of the skin in Vertebrates is inconsistent with an Arthropod 

 ancestry; 3. the differences in the eyes; 4. that objections to the Germ-layer 

 theory practically concern mesoblast alone, not epiblast and hypoblast; 5. that 

 the resemblance between the earliest vertebrates and the Palaeostraca is quite 

 superficial; 6. that Amphioxus is much nearer the original vertebrate than 

 is Ammocoetes and that Amphioxus is related to Balanoglossus and so 

 to the Echinoderms. 



Prof. E. H. Starling supported Gaskell's contention that the nervous 

 System is the factor of chief importance in specialisation. 



E. S. Goodrich maintaincd that the Vertebrata, Arthropoda and Mollusca 

 have all been evolved on fundamentally different and irreversible lines, and 

 emphasised the existence of nephridia with solenocytes in Amphioxus as proving 

 its relationship with the lower invertebrate Coelomata. 



Dr. H. Gadow criticised current theories of Vertebrate segmentation, 

 and rnaintained that Gaskell's hypothesis of the origin of the skeleton and 

 notochord of vertebrates is the best yet put forward. The Germ-layer theory 

 is discredited, and with it the view that the one System homologous throughout 

 the animal kingdom is the alimentary canal. 



Dr. Smith Woodward said that the earliest vertebrates had left no 

 fossil remains, and that therefore palaeontology afforded no clue. The supposed 

 appendages of Ostracoderms are due to misinterpretation. 



Prof. A. Dendy criticised Gaskell's hypothesis on the ground that his 

 Interpretation of the relations of the eyes is incorrect. The retina of the 

 pineal eye is Compound, and not comparable with the median eye of Arachnids. 

 The development also is different in the two cases. The hollow central nervous 

 system of vertebrates is due to the need for increased surface and nutrition. 



Sir Ray Lankester reviewed the history of speculation on the ancestry 

 of vertebrates, and concluded that all the great Coelomate phyla had radiated 

 from a very primitive stock, and were not derived one from another. They 

 all inherited the same fundamental tissues, and detailed similarities were due 

 to convergence. He regarded Amphioxus and the ascidian tadpole, though 

 degenerate, as nearer the primitive stock than Petromyzon. 



Dr. P. C. Mitchell regarded the origin of the vertebrate nervous system 

 as one of several modes in which a diffuse sub-epidermal sheath has been 

 specialised. 



Prof. J. S. Gardiner pointed out that in this speculation we can only 

 argue from analogy and probability. From this point of view Gaskell's hypo- 

 thesis in the most striking yet put forward. Morphologists are liable to error 

 from their neglect of function, and physiological in addition to morphological 

 evidence is adduced by Gaskell. Doncaster (Cambridge). 



866) Bosanquet, W. C, A note on the spirochaete present in ulcera- 

 tive granuloma of the pudenda of Australian natives. 

 (Parasitology 2,4. p. 344—347. 1910.) 

 Spirochaeta aboriginalis ähnelt sehr der Spir. pertenuis. Schilling (Berlin). 



