668 THE AMERICAN NATURALIST. [VoL. XXXVI. 
the post-cardinal veins of the lower vertebrates is sketched, the 
instructive variations which these veins show is not even alluded 
to. lus, in many places the second volume shows deficiencies 
where, from the completeness of the first, one would expect to find 
an ample and well-balanced account. As in the first volume, so in 
the second there is a strong disinclination to accept the results of 
embryology. Though this is in some respects an advantage, for in 
the last twenty years embryological evidence has certainly been 
given much more weight than it should have had, still its almost 
complete exclusion is by no means a wise course. The account of 
the origin of the complex teeth of mammals and the question of 
the number of generations of teeth in this group, lose much by the 
omission of embryological facts. So, too, the discussion of the rela- 
tions of the pronephres to the mesonephros is left in a very unsatis- 
factory form because of the absence of embryological data. While 
embryology may have been too exclusively followed by many, its 
results are too important to be lightly cast aside. Notwithstanding 
the defects that have just been pointed out, the volume before us 
and its companion certainly represent the high-water mark among 
modern comparative anatomies of the vertebrates, and the author 
is to be congratulated on his good fortune in having completed a 
book that will bear comparison not only with the best of contem- 
porary work but with the best that has gone before. P. 
Animal Life in the Deep-Sea. — Professor Seeliger's? pamphlet 
of fifty pages presents a very readable popular account of the animal 
life of the deep sea. After a brief historical résumé of the growth 
of deep-sea investigations, the effect of the environment on the 
animals is considered. The icy temperature of the deeper waters 
is contrasted with the variable temperature of the surface. The 
influence of the enormous water pressure is well illustrated by com 
parison with that of atmospheric pressure. The presence of free 
oxygen and of carbon dioxide and the influence of the latter on 
skeleton building in deep waters are discussed. Finally, the absence 
of sunlight and its relation to the sense organs, luminous organs an 
food supply of the deep-sea animals is dealt with at some length. 
The account, though brief, is carefully compiled, and is followed by 
an excellent series of note references, in which some of the questions 
brought forward in the text are more fully considered. 
1 Seeliger, O. — Zierlebém der Tiefsee. Leipzig, W- aumente r9ol. 49 PP» 
1 Tafel. 

