No. 395.] REVIEWS OF RECENT LITERATURE. 895 
Lateral Fins of Fishes. — Professor W. Salensky’ has given a 
brief but important report on the development of the lateral fins 
of fishes. According to Gegenbaur, the lateral fins of fishes are 
derived from modified gill arches, and the fish in which the most 
primitive form of fin occurs is Ceratodus. Professor Salensky 
has studied the development of the lateral fins in the sterlet and 
in Ceratodus. In the pectoral fin of the sterlet the fifth to the 
tenth myotome produce muscle buds which give rise to the mus- 
culature of the fin. Myotomes posterior to these also give rise to 
buds which, however, abort. The fin rays do not produce basalia 
by the fusion of their proximal ends, but rays and basalia come 
from a common blastema. In Ceratodus the sixth to the tenth 
myotome contribute muscle buds to the fin. The skeleton of the 
fin appears in the form of a single rod of cartilage and the rays 
bud out from it without reference to the muscle buds. The rays are 
comparable with the secondary rays, not with the ordinary rays of 
the fish fin. The cartilage axis of the fin is homologous with one 
of the basalia. As the muscles of the Ceratodus fin arise as in 
other fishes, it is fair to assume that the Ceratodus fin is not a primi- 
tive fin, as Gegenbaur believed, but is a greatly reduced fin of the 
ordinary type. These facts in large measure destroy the slight sup- 
port that Gegenbaur’s archipterygium theory formerly had. 
i a P 
The Chiasma of the Optic Nerves of the Amphibia has been 
studied by Franz Fritz (Jen. Zeit., Bd. XXXIII, p. 191), both by 
microscopic and by degeneration methods. His most important 
result is that there is a total crossing of the optic nerves. Professor 
Kolliker has lately confirmed several of the results of Ramon y Cajal 
as to the existence of numerous unilateral and direct fibres in the 
chiasma of certain mammals ( Verhandl. Anat. Ges., Bd. XIII, 1899), 
and the fact that in some cases fibres divide in the opticus, and the 
two branches go to the two tracts. 
Eigenmann on the Blind Fish of the Caves. — One of the most 
valuable contributions yet made to the literature of Organic Degen- 
eration -is a paper entitled ‘‘ The Eyes of the Amblyopside,” being 
the first of a series on “ The Eyes of the Blind Vertebrates of North 
America,” by Dr. Carl H. Eigenmann. It is published in Roux’s 
1Salensky, W. Zur Entwicklungsgeschichte des Ichthyopterygiums, Proc. 
Fourth Internat. Congress Zoöl., pp. 177-183. 1899. 
