116 Organs of Hearing in Mollushs. ['!rZrnIi, rlrrff ' 
organs under its control, while in the pedal ganglion resides the 
locomotor faculty. 
The fact of the variable positions and relations of the otolites 
had served as an argument against the " law of connections." My 
aim has been not to raise at this moment the grave question of the 
absolute fixity of those connections ; but it is hard to avoid remark- 
ing how futile it is, in complex questions of zoological philosophy, 
to found general deductions on very minute details. 
In assuming in Gastropods an organ of sense to be sometimes 
in connection with a motor and sometimes with a sensory ganghon, 
there resulted an exception to the " principle of connections " — of dis- 
tinction between sensibility and motricity. But in reasoning thus, 
the same process was followed as that used for vertebrate animals 
before the discoveries of Bell and Majendie. 
Certain connections have an invariable fixity. Morphological 
transformations alone can cause them to be misinterpreted. The 
study of the morphology of organs founded on the constancy of cer- 
tain true relations should lead the malacologist to recognize "des 
parties destinees a lui fournir les caracteres zoologiques destines 
a la specification." 
In conclusion, it is demonstrated by my researches that the 
connection of certain parts of the nervous system of moUusks being 
fixed, sensibility and motricity are fixed in all the Cephalophora as 
in all vertebrates. 
Ulnstitut, No. 1821. 
