The Morphology of Functional Activity in the Ganglion cell.s etc. 487 
ties of a primitive animal with those so high in the scale was obviously 
the next Step and at the personal Suggestion of Geheimrat Professor 
Richard Hertwig whose doctrine of the nucleus-plasma relation as 
applied to the nerve cell has been the underlying foundation for whatever 
of a logical and rational nature the Interpretation of the morphology 
possesses, the crayfish was adopted for Investigation. 
AVliile the usual advance of knowledge is from the simple to the 
complex, it wUl give a more desnable viewpoint of the present work 
to emphasize the fact that in certain respects the nerve ceU represents 
an exception to this course. Comparing the primitive cells of Camlarus 
and the specialized Purkinje cell, the shifts in morphology are vastly 
more striking, more inclusive in the latter, and so correlated that their 
significance is more open. So true is this that, in the opinion of the 
writer, any full Interpretation of the nature of the reaction in the 
primitive cell without the light shed by the other would have been 
exceedingly more difficult, if not doubtful. That this has a bearing 
in relation to certain opinions deduced from primitive cells alone wUl 
be made apparent. 
Source of Material. 
For the identification of the specics of crayfish used as Camharus 
virilis, I am indebted to my colleagues in Zoology. The material from 
fortyfive animals of all ages and from fifteen embryos at term and new- 
born has been used. The material includes animals directly or recently 
removed from their normal habitat and others subjectcd to experimental 
activity. The main part of the study was devoted to the former. This 
was of course the more important as the main point is that the experi- 
mental animals differ only quantitatively, in the degree and extent of 
their changes. It was found to make no appreciable difference as regards 
the average animal for reasons which wäU be apparent later, but the 
normal animals from which the bulk of the measurements were made 
were küled on the bank of the stream as soon as caught and the material 
at once fixed. This is the reason their weights are not given though 
their comparative size was carefully noted. However, this refers to 
a period of a day or so. It evidently makes a marked difference if the 
animals are kept for weeks in an unusual environment in the labora- 
tory, without imitating natural conditions closely, even though they 
are well fed and have a continuous supply of fresh water. The season 
of the year will be shown to make a profound difference in the normal 
33 * 
