291 
Dourn’s memoir is illustrated by seven beautifully executed plates ; 
regarding these I hope to be believed in stating that very many of 
the figures were very familiar to me as revealing facts independently 
discovered by me, and chiefly in Raja. 
After a divergence on some questions in neurogenesis, which has 
existed for over six years and dates from the publication of my work 
on the “Branchial sense organs etc.”, Donen and I are finally coming 
nearer to agreement. 
To conclude the similarity of the fields of our labours one must, 
indeed, go back to the memoir just cited. 
For the past two years and more it has been my endeavour, 
aided by a collection of about 300 Raja embryos of all ages and 
sizes, and in so far as other duties afforded the requisite leisure, to 
extend the work before mentioned, to study the relations and histo- 
genesis of ganglion cells and nerves, and to obtain a deeper insight 
into the nature of the transient or larval nervous apparatus of ovi- 
parous Ichthyopsida, which I described in a preliminary paper in 
1889.1). 
Dourn’s memoir begins with the consideration of histogenetic 
problems connected with the branchial or lateral sense organs and the 
mode of origin of ganglionic and nervous elements from them. This 
portion of the work goes over, certainly in many respects in more 
detailed manner, much of the ground covered by my former paper. My 
more recent researches have yielded additional facts and conclusions 
as to the lateral sense organs, their nerves, ganglia etc. similar to those 
recently published by Donrn. 
Studie 17 does something more than treat of the subject matter 
of my previous work; i also, while extending, confirms my former 
results. Naturally this can be none other than a source of satisfaction, 
and all the more in that since 1885 Prof. Domrn has seldom omitted 
to use any opportunity which offered of denying the justification of 
the till now peculiar and isolated position taken up by me on this 
question. 
It might weary the reader, and would certainly take up space, to 
cite the various passages bearing on the matter in the “Studien”, be- 
persistent larval apparatus, i. e. one curried over into the service of the 
adult. It would appear to be at any rate partially, if not completely, 
homologous with that of Elasmobranchii. Naturally I doubt the sensory 
function which Frrrscw would ascribe to it. 
1) “The early development of Lepidosteus osseus”. Proc. Roy. Soc. 
London, Vol. 46, 1889. 
