- tA Ree ANH Zu UL imp) RONMENT n 
1894.] Recent Literature. 943 
RECENT LITERATURE. 
Amphioxus and the Ancestry of the Vertebrates.'— This 
important monograph will be welcomed by all students of zoology as 
as a valuable accession to the literature of the theory of descent. 
More than this, the volume bears internal evidence throughout of pains- 
taking care in bringing together, in an exceedingly readable form, all 
the essential details of the structure and metamorphosis of amphioxus 
as worked out by anatomists and embryologists since the time of Pallas, 
its discoverer. The interesting history of the changes it undergoes 
during metamorphosis, especially its singular asymmetry, is clearly 
described and ingenious explanations of the phenomena are sug- 
gested 
Most important, perhaps, are the carefully suggested homologies of 
the organs of Amphioxus with those of the embryos of the vertebrates 
-above itin rank, especially those of the Marsipobranchs and Selachians. 
Though the comparisons with the organisms next below amphioxus, 
‘such as the Ascidians, Balanoglosus, Cephalodiscus, Rhabdopleura and 
the Echinoderms, will be found no less interesting. In short, the book 
may be commended to students already somewhat familiar with zoolog- 
ical facts and principles, as an important one to read. They may thus 
be brought to appreciate to what an extent the theory of descent is 
indebted to the patient labors of the zoologists of the last forty years 
for a secure foundation in observed facts, seen in their proper correla- 
tions, according to the comparative method. 
The figures are good and there is very little that can be adversely 
criticised in the book. On page 176 it is stated that the ectoderm is 
not ciliated in any craniate vertebrate. To this statement exception 
must be taken in regard to the ectoderm of the sides of the body and 
especially the tail of young tadpoles just hatched. Born in his experi- 
ments, in grafting pieces of young tadpoles upon one another, found 
that the tail,when cut off and lying on its side, had a power of 
movement, in the cephalad direction, that could be explained only 
-on the supposition that the ectoderm of the sides was more or less ex- 
tensively covered with cilia. This observation the writer has confirmed 
in repeating Born's experiments in just hatched tadpoles of Rana. The 
! Volume II of the Columbia University Biological Series, by Arthur Willey, 
B.Sc. 8vo, pp. 316, 135 figures. New York, MacMillan & Co., 1894. 
