ZOOLOGY: AREY AND CROZIER 
499 
The polarity evident in these reactions of the single gill plumes has 
certain fundamental resemblances to that seen in the tentacles of sea 
anemones.^ Like the latter, it pertains to other than tactile forms of 
activation (e.g., shading), is obliterated by magnesium sulphate anaesthe- 
sia, and persists in all its aspects in the plumes of an excised gill-crown 
(tied off basally to preserve internal pressure). It is therefore a local 
matter, conditioned by a self-contained nervous structure which con- 
ducts impulses more easily distalward than basally. The nature of this 
autonomous nervous equipment is defined by the fact that strychnine, 
in concentrations amply sufficient to affect certain other responses of 
the nudibranch known to be mediated by the central nervous ganglia, is 
without influence upon the responses of the gill plumes. The type of 
nonsynaptic conducting mechanism (nerve net) which is thus indicated 
for the gill crown, we attribute, on similar evidence, to all the peripheral 
parts of Chromodoris. 
If the oral tentacle of one side of a Chromodoris be stimulated, the 
homolateral dorsal tentacle ('rhinophore') contracts together with the 
activated tentacle; the opposite oral tentacle does not respond. If 
however a 'rhinophore' be stimulated, the tentacle of the same side does 
not react with it, nor does the other 'rhinophore' respond. The same 
homolateral nature and irreciprocal character of nervous transmission 
between the several reacting parts is further found in a detailed study 
of the activities of the mouth and protrusable pharynx, tentacles, 'rhino- 
phores,' and the anterior edge of the foot. Conduction such that a 'rhin- 
ophore^ responds when its homolateral tentacle is stimulated disappears 
when the supra- and suboesophagal ganglia have been removed. 
Under the influence of injected strychnine solution, we find that these 
reactions involving central, inter-organ transmission are profoundly 
modified. In general, the threshold for such reactions (now followed by 
a relatively long 'refractory interval') is lowered, the responses them- 
selves enhanced. The irreciprocal character of the conduction, as be- 
tween tentacle and 'rhinophore,' is abolished; so likewise is the normally 
pronounced homolateral bias of the reactions obliterated. There are 
other additional evidences of facilitated intraganglionic communication 
under strychnine. These effects are not manifest in deganghonated 
individuals treated with strychnine.^- 
It may therefore be assumed that peripherally, in the body wall and 
its projecting outgrowths, there are nerve-nets concerned with local re- 
sponses; that these nets are characteristically polarized; and that they are 
dominated by the central nervous system of the nudibranch, the latter 
