BY J. T. WILSON AND C. J. MARTIN. 663 



we have described, and, so far as they go, to carry conviction of 

 the realty of the things represented. And after all it may well 

 enough be doubted whether a blurred uncertainty of pictorial 

 representation is so very greatly inferior to that fatal illusory 

 clearness of delineation so often met with, which is due to the 

 influence of inadequate visual hypothesis upon the draughtsman. 

 Such clearness may indeed be advantageous where no possible 

 doubt exists as to the nature and characters of the structures to 

 be represented, since these may in this way be made perfectly 

 clear to the student; but on the other hand it is only too common 

 to find erroneous hypotheses as to the nature of obscure structural 

 details backed up by misleading drawings of the " clearest " 

 possible description. And this observation is not made hei^e 

 simply as of general application. If the reader will refer to Mr. 

 Poulton's own figures (especially his fig. 12 of PI. xiv.) showing 

 the structure of the " ganglion " in relation to a sweat-duct in the 

 skin of the platypus snout, he will there see represented a collection 

 of bodies described as " ganglion-cells," each of which is figured 

 as duly equipped with a definite nucleus. As a matter of fact, 

 as we shall show later on, these ai'e not ganglion cells at all, but 

 knob-like endings of medullated nerves, — and they do not possess 

 nuclei. The appearance in a few of these bodies of a spot (to 

 be further referred to) more or less suggestive of a nucleus, (and 

 in some few cases, perhaps, the actual presence of a nucleus 

 belonging to the sheath of the somewhat cell-like mass) has 

 evidently been misinterpreted by Mr. Poulton as witnessing to 

 the existence of nuclei in the bodies themselves. Nuclei have 

 accordingly been clearly delineated so as to convey a quite 

 inaccurate idea of the real nature of the "ganglion" in connection 

 with the sweat-duct. 



We are, it is needless to say, quite disposed to take for granted 

 that Mr. Poulton's material was not of the best description, and 

 did not afford a fair opportunity for correctly interpreting the 

 details of these nerve structures. But what we complain of is 

 that he has given to his drawings an utterly misleading character 

 of clearness and definiteness by representing structural features 



