SCIENTIFIC SUMMARY. 
235 
motor plate ” (plaque motrice'), at tlie extremity of tlie cylinder axis. 
2. Tlie union of the nervous element with the muscular bundle is accom- 
plished in the following manner. When the muscular bundle is provided 
with sarcolemma, and the nervous element with a sheath, this latter becomes 
fused with the envelope of the primitive muscular bundle, at the point 
where the nervous element meets the muscular bundle. At this same point, 
or a little before, the medullary substance stops, whilst the cylinder axis pur- 
sues its course, and penetrates the “ motor plate.” 3. The motor plate is 
placed beneath the sarcolemma. It presents usually the form of a cone, with 
its summit directed to the side of the nerve-tube, whilst the base is applied 
to the primitive muscular fibres. 4. This plate is formed by two superposed 
and very distinct layers, especially in those animals provided with large 
‘^plates,” as, for instance, ;n the torpedo. The substance of the superior 
layer is granular, that of the inferior layer is perfectly homogeneous, and 
probably it is nothing more than a thickening of the cylinder axis. 5. In the 
substance of the granular layer of the plate is found, in the torpedo, a system 
of canals, in which the cylinder axis ramifies, forming a coarse network. 
These canals are limited by a sheath, which forms their walls. 6. When the 
muscular bundles possess a central canal, the granular substance of the plate 
is continuous with the granular substance contained in this canal. 7. In 
animals provided only with smooth muscular fibres the cylinder axis traverses 
the granular substance of the plate, dividing itself into two filaments, which 
pass to the two extremities to terminate in the points of the contractile 
element. 8. Everything tends to the belief that each primitive muscular 
fibre has but one motor plate. In this, one or several nervous elements can 
terminate, arising from the subdivision of one and the same nerve-tube. 
9. The diameter of the motor plate augments in proportion to the thickness 
of the primitive muscular bundle. 
Fishes of the Iberian Penmsida is the name of a paper read before the 
Austrian Academy by Herr Steindacher. This fauna includes 69 species, 
belonging to the following 9 families : — Berycidae, Percidae, Scienidae, Pristi- 
pomidae, Sparidae, Mullidae, Triglidae, Trachinidae, and Trichiurida. Seven 
of the 69 species have been for the first time added to European Ichthy- 
ology. The author stated that his observations convince him that many of 
the so-called specific characters of fishes, especially of the Mediterranean 
basin, are based upon sexual difierences, and are therefore dangerous and 
unreliable. — See Report of the Meetings of the Vienna Academy for October. 
Parasitic Crustacea. — In one of the numbers of the American Journaly 
Mr. Verrill describes a curious instance of crustacean parasitism. He says, 
in examining some specimens of sea-urchins from the coast of Peru, he 
observed that in many instances the anal contour was imperfect, or very 
much deformed. An examination of the interior in these cases detected the 
presence of a minute Crustacea (Fahia Chilensis) analogous to that found in 
the oyster. It was attached to the lower portion of the intestines, and was 
enclosed in a species of cyst. The Crustacea found were, in nearly every 
instance, females laden with ova, and it seems as though, when once they 
enter, they are compelled to remain prisoners for life. In all probability the 
parasite enters when very small, by the anal aperture, and by its constant 
growth and consequent pressure on the shell disturbs this latter. 
VOL. VII. — NO. XXVII. R 
