l88o.] Analyses of Books * 467 
form, corresponding to new perfection of work in the animal 
machine. In Degeneration there is suppression of form, corre- 
sponding to the cessation of work.” The author recognises that 
elaboration of one organ may be, and often is, the accompani- 
ment of degeneration in others. An animal is only to be viewed 
as an instance of degeneration when it is, as a whole, left in a 
lower condition than that of its ancestors. Prof. Lankester 
considers that any new set of conditions which secure the food 
and the safety of any animal without effort lead as a rule to 
degeneration. 
Some curious instances of degeneration are given. Among 
others the barnacle, a degraded crustacean, classed by Cuvier 
and others among molluscs, and only restored to its rightful rank 
in consequence of the discovery of its juvenile stages of form. 
The Ascidians the author regards as degenerate Vertebrates, a 
conclusion justified by the researches of Kowalewsky on their 
development. They pass through a tadpole state almost iden- 
tical with that of the common frog, but instead of being 
elaborated they degenerate. The Convoluta worms, which con- 
tain chlorophyll, and have the power of nourishing themselves, 
like plants, upon the carbonic acid dissolved in the water around 
them, are also adduced as an instance of degeneration. As the 
chief causes of such structural degradation the author enume- 
rates parasitism, immobility, vegetative nutrition, and excessive 
reduction in size. Where these conditions are present degene- 
ration may be suspefted, even in the absence of any embryo- 
logical evidence. 
Finally, it is shown that degeneration is not a mere geological 
question. In vegetable life it plays, as might be expeaed, a 
decided part. In language it has long been recognised, and it 
must be taken into account in anthropology and in social science. 
Prof. Lankester hints at the possibility of a degeneration in what 
are at present the leading types of mankind. Who can venture 
to pronounce such a decay out of the question ? 
The hypothesis of degeneration is worthy of very careful 
study, and we must consequently recommend this thoughtful 
and suggestive treatise to biologists. 
Letter of the Commissioner of Agriculture on Sorghum Sugar . 
Washington : Government Printing-Office. 
A pamphlet recommending the cultivation of sorghum in the 
United States as a source of sugar, and giving descriptions and 
figures of the machinery required for extraaion. 
