412 TRANSACTIONS OE SECTION D. 



it seems reasonable to conclude that they are spawned pelagically without 

 ever having been near the bottom, which is, in fact, 4,000 to 7,000 

 metres from the surface. How far from the surface the mursenoids 

 actually spawn is a question which will be very difficult to solve, as we 

 lack apparatus for the capture of large and swift pelagic fishes. 



You will see from what I have said that our investigations have not con- 

 firmed the earlier suppositions, that the larval development of the eel-fishes pro- 

 ceeds at the bottom of the sea or in great depths. On the contrary, in the 

 species we are at present acquainted with it proceeds in the uppermost layers. 

 The fact also that such large quantities of munenoid eggs are found at the 

 surface, both in the Mediterranean and the Atlantic, indicates that the same 

 holds good for various other species of eel-fishes. 



The charts and preparations exhibited show how far we have come in our 

 investigation of the two eel species which are of the greatest interest for us 

 here in North Europe, the conger and the eel. In the case of the conger, we 

 have come so far that we have all stages, even the youngest, and only the eggs 

 remain to be identified. But in the case of the fresh- water eel, the smallest 

 stages we have found are already over 4 cm. It is therefore impossible as yet 

 to say where the eel spawns in the Atlantic, except that it must be outside the 

 continental slope. Regarding the conger, we know so much more that we can 

 say that it spawns in any case everywhere in the Mediterranean and in the 

 Atlantic west of the Mediterranean. 



How far to the west in the Atlantic, I do not know ; I can only say that the 

 place furthest west where we have found the full-grown larvae of Conger vul- 

 garis, lies at 30° W. longitude, in the neighbourhood of the Azores. 



I shall not enter upon further details at present. You will have seen that 

 there is still much to explain in these problems, but you will perhaps also have 

 obtained the impression that the question of the biology and reproduction of 

 the conger and eel is extremely difficult, much more complicated than it seemed 

 to be after the publication of the Italian discoveries. It has only been with the 

 help of our good ship and our good apparatus that we have been able to win 

 any result from these prolonged investigations. One way or another we hope 

 to continue these, and thus be able to make still further progress. 



4. Note on the Occurrence of Ampliidinium. 

 By Professor W. A. Herdman, F.R.S. 



5. The Lantern of Aristotle as an Organ of Locomotion. (Echinus escu- 

 lentus and E. miliaris.) By James F. Gemmill, M.A., M.D., D.Sc. 



I. Action out of water. II. Action under water. III. Other allied activities. 

 IV. Methods of observation. 



Summary. 



I. Reference to previous account by Romanes and Ewart. There occurs a 

 rhythmic swinging movement of the lantern. Progression is by a series of steps 

 or lurches which are more or less sharply defined. In each step the urchin is 

 raised on the tips of the teeth and a forward impulse given, (a) by strong 

 pushing or poling on the part of the lantern, (6) by similar but usually less 

 effective pushing on the part of the spines, and (c), after a certain stage, by the 

 influence of gravity. The lantern is then retracted and the teeth swing forward 

 into position for initiating a new lurch. Length and rhythm of step in urchins 

 of various sizes. Recording surfaces. Inversion, equatorial section, and load- 

 ing experiments. Muscles involved. Relation of rotation to progression. Causes 

 of rotation. Locomotion possible even in the absence of spines. 



II. Lantern not needed for ordinary locomotion over more or less horizontal 



