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SCIENCE. 



[N. S. Vol. XI. No. 271. 



had hitherto been done the early separation 

 of the mesonephric from the metanephric 

 kidney, and he first showed the essential 

 relations of the permanent kidney and its 

 ureter to the mesonephric duct. 



Another of his histological works deals 

 with the structure of the stomach, in this 

 in a measure preparing a way for the ex- 

 haustive comparative studies of his stu- 

 dent, Professor Oppel. Other contributions 

 relate to the development of the liver, 

 spleen and pancreas (in Ammocoetes) and 

 afford striking evidence that these organs 

 are closely related genetically. Further 

 papers discuss the characters of muscle 

 cells, and the origin of blood in the valves 

 in the dorsal vessel of the leech {Rhyncho- 

 hdella). In his earlier work he was also at- 

 tracted into the puzzling field of the electric 

 organs in fishes ( Gymnotus, Mormyrus and 

 Malapterurns') , 



Another and perhaps the most impor- 

 tant line of his histological work relates to 

 the structure of nerves. He thus demon- 

 strated that the axis cylinder was not a 

 solid structure in the sense of the earlier 

 investigators. This condition he showed 

 was artifact : the ' cylinder ' is rather to be 

 looked upon as an axial canal containing 

 in its fluid contents the delicate fibrils. In 

 the matter of the central origin of nerve 

 fibers his further observations have yielded 

 a basis of the new neurone theory. The 

 difficult question as to the exact mode of 

 termination of nerve cells in an end-organ 

 he also successfully answered in one of his 

 earlier papers ; in the salivary gland 

 (Blatta) he was able to trace the final arbo- 

 rescence of the nerve filaments on the wall 

 of the gland cell and he described the dis- 

 coidal enlargement at the tip of each fibril. 



Von Kupffer had never played the role 

 of a pioneer in any extended field of em- 

 bryological research. He has done the 

 work — which has only too often the greater 

 value — of extending, correcting and inter- 



preting the results of earlier observers. 

 Thus his famous work on the development 

 of the Ascidian was in the path which had 

 been opened by Kowalewsky, whose results, 

 as von Kupffer himself notes, were then al- 

 most universally discredited. Von Kupffer 

 soon came to support the new cause and he 

 even outdid Kowalewsky himself in advoca- 

 ting the closer affinities of the ascidians and 

 chordates. He thus showed in the ascidian 

 the continuity of the cord and brain, the 

 ' segmentation' of the tail, the presence of 

 'spinal nerves,' and the distinctly chordate 

 character of the notochord, together, later, 

 with interesting homologies in the sense 

 organs. And so too in his extended paper 

 on the development of the Lamprey he 

 took up the unfinished work, and succeeded 

 in reconciling several discrepancies in the 

 results of Max. Schultze and Shipley. But 

 it should be understood that the results of 

 pioneer investigators were to von Kupffer 

 but as the^foundation stones of detailed and 

 original work. Thus in his paper on the lam- 

 prey he soon laid aside his purely critical 

 studies and [attacked a series of difficult 

 problems relating to the origin of the mouth, 

 the cranial nerves, and of the primitive con- 

 ditions of the central nervous system. 



Gastrulation is one of the most difficult 

 processes with which the student of the de- 

 velopment of vertebrates has to deal. And 

 it is upon this theme that the work of von 

 Kupffer has thrown no little light. It was 

 formerly thought — and this was the rock 

 which wrecked the results of Pander, Baer, 

 and Rathke — that in the large yolk-filled 

 eggs of such animals as reptiles and birds 

 the germ-layers of the embryo arise one 

 from the other by a process of splitting 

 (delamination). Von Kupffer, however, 

 was able to demonstrate that in these forms 

 a process of infolding occurs, modified, it 

 is true, but proving that the gastrulation 

 of the higher forms is clearly homologous 

 with that of the^amphibia and manj^ fishes. 



