174 William Sörensen 
of the result of my examinations of these organs I used for the 
sake of convenience a comparison: »a mechanism, which, by the 
way in which it operates, bears the greatest resemblance to the 
brake of a wheel — for instance, that of a railway carriage«. And 
this is, in the fewest possible words, the principle of all the me- 
chanisms of fixation which I know in any fish. 
»In order to render it possible for the spine to be moved back- 
wards, when fixed, the fixation must be caused to cease. This result 
is brought about in different ways in the three genera. In Syno- 
dontis there are a pair of short and thick muscles, m/, which arise from 
the side of the processus spinosi of the first and second free verte- 
bree (v°~*), and whose short and rather thick tendon melts together 
with the sheath [of strong and tight connecting tissue, vg] which 
encloses the branches of the rudimentary ray [each in its sheath] 
so that the tendon forms a thickened part of the front-wall of the 
Sheath. If you pull at this muscle, the fixation will cease — even 
if with the other hand you press backwards the spine (not too for- 
cibly) — the rudimentary ray being swung forward [without 
being moved out of its place] and its naked faces being carried 
away from those of the roof-like keel, so that now the spine 
as with a jerk can be carried backwards.« (My book, pag. 13—14.) 
In both memoirs of Dr. TmıLo’s, that which according to me is 
the real diarthrosis of the rudimentary ray remains unmentioned as 
well as the muscle m/, and according to him the scouring faces 
form the diarthrosis (the »Gelenk«). In his first paper he says in 
a general way: »... diese zwei Fischarten [Synodontis and Gaste- 
rosteus| zeigen an ihren Stacheln nichts Anderes als eine Art von 
Kegelgelenk, dessen scheinbar höchst eigenartiges Hemmvermögen 
bloß eine höher entwickelte Eigenschaft der bisher beschriebenen 
Kegelgelenke ist. Diese auf den ersten Blick wohl nicht ganz ein- 
leuchtende Behauptung glaube ich am besten zu begründen, wenn 
....« As his recent paper is to be found in the preceding volume 
of Morphologisches Jahrbuch, it is sufficient to refer the reader to 
the paper itself, pag. 309—318. 
When Dr. Taito says (pag. 352) with regard to me: »Er meint, 
das Gelenk des ersten Strahles der Riickenflosse von Synodontis sei 
(The Journal of Anatomy and Physiology. Vol. XXIX. Edinburgh 1895.) — 
On this paper has been rendered an account in: Zoolog. Centralblatt. 1896. 
No. 21. Unfortunately, this account is in several points anything but correct. 
