GASTROPOD PROTOCONCH. 183 
The Ontogenetic Stages represented by the 
Gastropod Protoconch. 
By 
H. Leighton Kesteven. 
ContTENTS. 
PAGE 
A. INTRODUCTION . 5 a : F 183 
B. A ConcHOoGENETIC Wukkeon urns : ; ce RIREE 
C. APPLICATION OF THE NOMENCLATURE . 185 
D. A Depuctive Metuop or STUDYING THE Rinne ame 
HistoRy oF A GASTROPOD . F : a sé 
A. INTRODUCTION. 
That the so-called “protoconch” may not be the true 
protoconch has been known ever since Lankester (7) drew 
attention to the fact that the primitive shell-sac or gland 
sometimes became filled with a chitinous plug which was sub- 
sequently shed, before the inception of the protective shell. 
The shell which is formed immediately subsequent to this 
is that which conchologists generally have termed the pro- 
toconch ; but this also may be shed, and leave behind it an 
apex, perhaps of several whorls, which differs materially from 
the rest of the shell, which apex has in turn been treated as 
a protoconch. 
From a study of the subject extending over several 
years, 1 have come to the conclusion that a Gastropod pro- 
toconch may have been formed during one or more of four 
stages of growth, and it is even conceivable that it may 
in some instances consist of portions formed during all four. 
These four ontogenetic stages are: The typembryonic, 
phylembryonic, nepionic, and ananeanic, and the portions 
of the conch formed during each may be advantageously 
VoL. 49, part 1.—NEW SERIES. 14 
