176 THE AMERICAN NATURALIST. [VOL XXXV. 
in a tentative manner, but further advance, or even the 
confirmation of steps already taken, could be made only on 
the basis of observed facts of development in concrete cases. 
Munier-Chalmas (1895) propounded certain theories of proto- 
typic hinges, but in the absence of published observations 
these attracted slight attention. In the same year the writer 
elaborated his previous thesis, insisting on the modifications 
due to dynamic causes acting directly on the hinge, on the 
origin of hinge teeth from initiative due to external sculpture 
in the dorsal region, and on the duplex nature of the so-called 
ligament, which many years before had been recognized by 
Récluz, whose observations fell on sterile soil. The existence 
in many nepionic bivalves of a primitive hinge, since named 
the provinculum, was also pointed out. Almost simultane- 
ously the first of Bernard's papers appeared, for the first time 
furnishing facts in relation to the development of the hinge 
teeth in a comparative series of different genera ; and thence- 
forward, until the time of his premature decease, he continued 
to bring together invaluable data in the same line, covering a 
large number of genera and opening the way to a field of 
research of extraordinary promise, throwing an entirely new 
light on the development of hinge structure and making a 
permanent breach in the barriers of a conservatism which had 
so long retarded the appreciation of efforts for a more scientific 
consideration of the facts of hinge structure. As in all first 
attempts, the shackles of outgrown methods were not wholly 
discarded, and much more study is required before a final 
system can be hoped for, but so much has been done that it is 
no longer possible for the former inertia to prevail. Several 
papers bearing on this subject have recently appeared. One 
of them, by W. von Vest,! can be briefly dismissed, as it con- 
tributes nothing new in the way of facts and is chiefly devoted 
to the introduction of a host of new technical German terms, 
which in turn are reduced to symbols, which when formulated 
; Ueber die Bildung und Entwicklung des Bivalven-Schlosses, followed by 
Entwurf einer Einteilung der lebender Bivalven nach dem Schlossbau, Verh. des 
Siebenburgischen Vereins für Naturw. zu Hermannstadt, Bd. xlviii (1899), pp- 
25-150, Pls. I-II. 
