PRESIDENTIAL ADDRESS, 531 
but stationary, the rostrum playing the part of a pile by which they were rooted 
in the mud at the sea-bottom, like the pointed base of a Flabellum or other 
deep-sea coral, or the anchor-spicules of a glass-rope sponge. In favour of this 
view may be adduced the size, weight, and solidity of the rostrum, which, if the 
animal moved about in a horizontal attitude, would have thrown its centre of 
gravity too far towards that end of the body: its circular section, which points to a 
radial, not a bilateral, symmetry, and hence, as above mentioned, to a sessile rather 
than a free-swimming habit. The pointed form of the rostrum would be admirably 
adapted to fixation in a muddy bottom, whilst its weight would render it a very 
effective anchor. Further, it is to be noted that Belemnites are found abundantly 
in strata of argillaceous origin. 
This view has a strong recommendation in the fact that it presupposes gradual 
progress in the Cephalopoda in the direction of greater mobility as evolution 
advanced, thus :— 
A. Orthoceras—firmly attached. 
B. Belemnites—anchored in the mud. 
C. Recent Dibranchiata—free-swimming. 
In regard to the question thus raised of the origin of the present race of 
pelagic Dibranchiates with (comparatively speaking) rudimentary shells, attention 
may be directed to a very remarkable and interesting memoir which has just 
appeared (May 17 of this year) by Dr. Werner Marchand (31) of Leipzig. This 
contains a descriptive and comparative account of the male internal conducting 
apparatus, shows how in all cases this may be referred to a common plan of 
structure, and finally reaches the conclusion that ‘the living pelagic Dibranchiates 
with separated sexes and vestigial shells were derived from non-pelagic herma- 
phrodite ancestors with elongated bodies and elongated shells.’ How far back in 
time we must travel to find these hermaphrodite ancestors is, of course, unknown ; 
whether they could be found among Orthoceras and its allies we have at present 
no means of ascertaining. Although many authorities believe that certain 
differences in the shells of Ammonites indicate sexual differences, there is not, 
so far as I am aware, any evidence of such in the Orthoceratitidee. 
Another interesting discovery of Professor Jaekel (18) is that of a slab of 
Solenhofen stone, upon which are certain specially arranged impressions, apparently 
made by the hooks on the arms of a Cephalopod. If this determination is correct, 
the fact is of the greatest interest, for it would show that these animals walked 
upon the ground with the head downwards and the distal extremity of the body 
elevated; that in them the arms were not merely morphologically, but also 
functionally, the equivalent of a foot. 
In conclusion let me direct your attention to a subject which is almost 
entirely the growth of the last fifteen years. I mean the discovery and investiga- 
tion of luminous organs in the Cephalopoda. ‘These have now been observed in 
no fewer than twenty-nine out of about seventy well-characterised genera of 
Decapoda, and have been found to present a most interesting variety in position 
- and in structure. 
Before passing on, however, to consider the structure of these organs it may be 
well to lay before you the evidence on the strength of which a photogenic function 
has been ascribed to them. The actual observations are remarkable chiefly for 
their paucity ; indeed, it may seem to some that the foundation of solid fact is too 
slender for the superstructure raised upon it, but still due consideration will show 
that this is not the case. The first recorded occurrence of phosphorescence in the 
Cephalopoda is due to Vérany (42), and dates back rather more than seventy 
years, though it was not published till 1851. The description is so definite and 
concise as to be well worth quoting :— 
‘As often as other engagements permitted, I watched the fishing carried on by 
the dredge on the shingly beaches which extend from the town of Nice to the 
mouth of the Var. On the afternoon of September 7, 1834, I arrived at the 
beach when the dredge had just been drawn in, and saw in the hands of a child 
MM 2 
