6 
cesses as superimposed flaps, each in shape of a child’s hand*. This 
comparison answers chiefly to the internal labial processes. 
The number of tentacles in those two pair of labial processes is not 
exactly the same in different specimens, nor even in the same speci¬ 
men at both sides. The description of Piumphius gives sixteen ten¬ 
tacles to the external labial processes, but does not mention their 
number in the internal processes. Prof. Owen found twelve tentacles, 
Prof. Valenciennes thirteen in each of those four processes. In the 
external processes Prof. W. Yrolik observed twelve tentacles on each 
side, as was observed also by me. The internal processes seem to 
have in general a somewhat larger number; Prof. Yrolik observed in 
this layer fourteen on each side ; I found also fourteen at the left and 
sixteen at the right side. The external labial processes are united in 
the mesial line at the ventral side above the funnel by a membrane 
with numerous fine folds on the inside ; the internal approach here 
nearer to each other and are united in a similar manner ; the commis¬ 
sure presents on the inside, towards the dorsal surface, seventeen or 
eighteen eminent, compressed, longitudinal folds, like the parallel 
ridges in the olfactory cavity of Fishes. This part is, according to 
Prof. Owen’s opinion, the organ of smell; but I believe that those 
folds are only rudimental digitations completing the circle of the in¬ 
ternal labial processes, and similar to the more numerous and smaller 
folds of the external circle, or even to the fringed margin of the lip 
round the mandibles. 
In respect to the observation of Valenciennes concerning the man¬ 
dibles, it is perhaps not unnecessary to note that I saw them in differ¬ 
ent specimens always covered with a calcareous white matter, as has 
been observed in the first accurate description of the animal by my 
eminent friend Prof. Owen. 
The sexual difference of the Nautilus requires still further elucida¬ 
tion. Prof. Owen’s description was relative to a female, and also all 
the other specimens observed by subsequent authors, or preserved 
hitherto in the museums, seem to be of female specimens. Hence it 
seems to follow that males are rarer; a similar circumstance of un¬ 
equal number has been noted in many other animals of several classes. 
The recent observations of Kolliker and some other authors haring 
elucidated the true nature of that abnormal animal form, not unlike 
to separated arms of Cephalopods, found in the shell of the (always 
female) Argonaut a, and formerly described as a genus of worm under 
the name of Hectocotyle by Cuvier, would lead us to expect similar 
males of the Nautilus living like parasites with the female in her shell. 
There exists however not the least indication in the different memoirs 
of Owen, Valenciennes and Yrolik, that such parasites were present. 
I can say that in Nautilus the sexual difference is not so great, and 
that the male lives in a shell like the female. I was fortunate enough 
to observe one specimen of a male, which was kindly presented to me 
by my colleague at the Faculty of Sciences of the Leyden University, 
the Professor of Botany, W. H. de Vriese. The differences it showed 
* “ Zijnde ieder lap gefatzoeneerd als een hand van een kind.” (Amboinsche 
Rariteitkamer, p. 60.) 
