118 GEORGE E. NICHOLLS - 
fiber, although undoubtedly a preformed structure, was certainly 
not a nerve fiber and, therefore, could not have the function 
ascribed to it by Sargent. In 1909, I published a statement to 
that effect and in the following summer, following my discovery 
of the practical accessibility of the fiber in the tail region, I 
carried out some experiments upon elasmobranchs, in an en- 
deavour to ascertain the function of the fiber. 
The results of these experiments, which were performed upon 
less than a dozen dogfish and rays, were hardly sufficient to give 
a conclusive answer to the question of the function of the fiber 
but were, nevertheless, extremely suggestive. An account of 
these experiments was published, therefore, in a short prelimi- 
nary paper which did not, however, appear until 1912. In 
the meanwhile, a much more extensive series of experiments 
had been carried out but there had been no opportunity to ex- 
amine this material microscopically before the paper in question 
was published. 
The completion of the investigation has been very considerably 
delayed, for these further experiments were scarcely completed 
when I left England to take up an appointment in India. I had 
purposed however, to carry on, there, the work of preparing the 
necessary serial sections. The material is, unfortunately, ex- 
ceedingly refractory, so that under the best of circumstances the 
preparation. of ‘serial sections demands much time and patience. 
In India, there were added difficulties, due to the climate, and 
the preparation of the sections went on very slowly, it being 
possible to attempt this work only during the cold weather. An 
attempt to get some of the material sectionized in England was 
unsuccessful, essential portions of some of the specimens being 
ruined in the attempt to prepare the sections and the remaining 
tails were returned to me as being too refractory to yield satis- 
factory sections by ordinary methods. In the end I was com- 
pelled to postpone the preparation of my remaining material for 
microscopic study until my return to England. Only recently 
has this part of the task been completed. 
In the interval, I have published a paper (12 a) dealing with 
the subject of Reissner’s fiber and its relation to the central 
