The originality of this volume is to reveal to the reader the
fascination of some unfamiliar sensory organs that are sometimes ignored
and often misunderstood. These receptors have only recently been
identified and their functional specificity is in some cases still a
matter for discussion. The four classes of sensory organs considered
here differ widely from one another in many respects. One might even say
that the only thing they have in common is that they belong to
cold-blooded vertebrates. These classes are: 1. the directionally
sensitive lateral-line mechanoreceptors of fishes and amphi- bians
(Chapter 7); 2. the pseudobranchial organs of some teleosts, equipped
with pressoreceptors and at least three other types of receptors (osmo-
and chemoreceptors) (Chapter 8); 3. the infrared-sensitive pit organs of
some snake families (Chapter 9); 4. the various kinds of
electroreceptors found in several marine and freshwater fish families
(Chapters 2 to 6). The first three classes of receptors mentioned above
thus rate only one chapter each, whereas five chapters are devoted to
the electroreceptors. Electroreception has aroused enormous interest
among physiologists in specialties ranging from molecular biology to
animal behavior. The resulting quantity of research and discussion fully
justifies this disproportion. However, it cannot be denied that the
contents of the volume must appear unbalanced and heterogeneous, yet it
should not be perceived as a mere juxtaposition of particular and
unrelated cases.