210 Miss Agnes Grane — On Certain Living and Fossil Fishes. 
resemblance between tbe enlarged plirangeal sac of Amphioxus and 
that. of tbe tunicated mollusks or sea squirts. He considered tbe 
lancelet also as allied to tbe annulosa, from tbe simple Organization 
of its respiratory and circulatory system, and M. Kowalevsky bas 
more recently traced a close affinity between tbis species and tbe 
early stages of some Ascidians. Thus, in Amphioxus are united 
cbaracters belonging to tbe Tunicates and Annelides, and unexpected 
relations are revealed between the Vertebrata and tbe Invertebrata. 
The Most Highly Organized Fish. — In tbe Lepidosiren, tbe 
bighest of all tbe fishes, we find an Organization of a no less complex 
nature. Tbe genus was fonnded in 1837 by Dr. Natterer for the re- 
ception of a singulär animal to wliich he gave the specific name of 
paradoxa, discovered by bim in America, inbabiting the swamps in the 
vicinity of the river Amazon. Tbis species, wbich attains a length 
of tliree feet, tbe body being eleventimes as long as the head, 1 is now 
becoming very rare. In 1839 Prof. Owen referred specimens from tbe 
river Gambia of West Africa to the same genus, under the designation 
of Lepidosiren annectens, and classed them in a provisional group 
between the reptiles and fishes. They are placed by Prof. Huxley 
in tbe bighest order of bis Classification of fishes, namely, tbe Dipnoi 
or “double breathers,” and are popularly known as “mud-fish.” 
These paradoxical “ scaled sirens” bave well-developed reptilian 
lungs co-existing with functional internal brancliiai, and are capable 
of living either in the water or out of it. Tbeir structure and 
habits are very peculiar. Düring tbe rainy season, tbe waters of tbe 
Gambia overtlow its banks, and tbe mud-fish is carried out of the 
true bed of tbe river. Wben the waters retire it is left stranded ; 
then, burrowing in the softened mud, it coils itself up, keeps open a 
communication with tbe air above its nest, and breathes by means of 
its modified swimming bladder. It tlius remains inactive tili tbe 
return of tbe floods soften tbe walls of its cell, wben it emerges, 
and resumes its former habits. They bave been found in a semi- 
torpid state eighteen inches below the surface, in situations where 
the ground is dry and hard for months in the year, and are dug out 
by tbe natives witb a sharp pointed stick and used for food. 2 The 
body of the Lepidosiren is fisli-like, and covered with small cycloid 
scales, simply constructed pectoral and ventral limbs are present, 
with a dorso-'caudal fin. The notochord is persistent, but the skull 
is partly bony, partly cartilaginous, and tbe costal arches and 
neural and hasmal spines are well ossified ; thus it forms a link 
1 Trans, of the Linnaean Society, vol. xviii. 
2 A specimen of L. annectens has been on exhibition in the entrance hall of the 
Brighton Aquarium for more than two years. It is kept at a regulär temperature 
of 70°, and is in a very thriving condition, having grown several inches since it has 
been in the institution, and thickened proportionately. The animal generally lies 
quietly at the bottom of its tank, rising occasionally to the surface to take in air. 
It is fed three times weekly on small pieces of raw beef, which it can be observed to 
eat in a very unusual manner. When the food is thrown in, the mud-fish Stretches 
itself leisurely and seizes it, as it comes within reach, between its sharply formed 
vomerine teeth. After masticating it slowly, it throws it out with a quick jerk, and, 
commencing at the other end, repeats the manoeuvre ; it then again rejects it, and 
subjects it to a third process of mastication before finally swallowing it. 
