280 THE ZOOLOGIST. 
introduced into this country by Huxley, as a basis from which 
extended studies can be made, and the present work is stated as 
designed to assist those further studies. The study of types is 
now an excellent and almost universal method, though Prof. Ray 
Lankester has recently proposed that a second course might be 
pursued in the study of ‘‘ exceptional, puzzling, and debateable 
animals,” by which significance of structure could be considered 
as the means of discussing affinities. : 
The classification is generally in agreement with that of the 
recent work of Parker and Haswell, but with some differences. 
Thus those authors appended the Nemerteans to the Phylum 
Platyhelminthes, whilst Prof. Sedgwick treats them as a distinct 
Phylum—Nemertea. He also considers the Polyzoa and Brachio- 
poda as constituting distinct Phylla, but which Parker and Haswell 
treated as classes of Molluscoida. These authors also placed the 
Mollusca after the Arthropoda, whilst in the work under present 
notice they follow the Rotifera. ‘The position of the Echino- 
dermata is also differently considered. We simply draw attention 
to the differences in method of these two notable publications 
because they have both appeared almost synchronously, and also 
because modern classifications are taken as representative of 
current views on derivation. 
Although this text-book is necessarily of a technical descrip- 
‘tion, there are stiil scattered some of those facts or incidents in 
life narratives so appreciated by the contributors and readers of 
this Magazine. As an instance, we may quote from the general 
remarks on the Mollusca. About 25,000 species are known, and 
are found in the sea to a depth of nearly 3000 fathoms. ‘ Their 
duration of life, where known, varies from one to thirty years; 
the Pulmonates generally live two years, but the garden snail © 
has been known to live five years. ‘The oyster is adult at about 
five years,and lives to ten years. The Anodonta do not arrive 
at sexual maturity till five years, and live for twenty or thirty 
years.” 
We shall await with interest the completion of the work. 
