468 NOTES 



father of Herpetology, and Owen of Odontology. Schleiden and Schwann 

 published their celebrated researches in cell structure, 1841; but Bichat, 

 who died 1802, was the founder of Histology. Protoplasm was discovered 

 by Dujardin in 1835, anc ^ called Sarcode. The name Protoplasma was 

 formally given to the slimy contents of vegetable cells by the German bot- 

 anist, Hugo von Mohl, in 1846. The essential identity of the protoplasm 

 of plants and of animals was first claimed by Max Schulze in 1861, who 

 thus made one of the most important generalizations in science. 



4 According to Mr. Darwin, the characters which naturalists consider 

 as showing true affinity between two or more species are those which have 

 been inherited from a common parent ; and, in so far, all true classification 

 is genealogical, i.e., it is not a mere grouping of like with like, but it in- 

 cludes, like descent, the cause of similarity. In the existing state of science 

 a perfect classification is impossible, for it involves a perfect knowledge of 

 all animal structure and life history. As it is, it is only a provisional at- 

 tempt to express the real order of nature, and it comes as near to it as our 

 laws do in explaining phenomena. It simply states what we now know 

 about comparative anatomy and physiology. As science grows, its lan- 

 guage will become more precise and its classification more natural. 



5 The term type is also used to signify that form which presents all the 

 characters of the group most completely. Each genus has its typical 

 species, each order its typical genus, etc. The word is also applied to 

 the specimen on which a new species is founded. A persistent type is one 

 which has continued with very little change through a great range of time. 

 The family of oysters has existed through many geological ages. 



6 The Coelenterata and Echinodermata together make up the Radiata, 

 the old subkingdom of Cuvier. Echinoderma is probably more correct - 

 than Echinodermata^ but we retain the old orthography. 



7 Strictly speaking, no individual is independent. Such is the division 

 of labor in a hive, that a single bee, removed from the community, will 

 soon die, for its life is bound up with the whole. An individual repeats 

 the type of its kingdom, branch, class, order, family, genus, and species, 

 through its whole line of descent. 



8 These definitions of the various groups are mainly taken from Agassiz. 

 They are not practically very useful, as they are not used by working natu- 

 ralists. The kind and degree of difference entitling a group to a particular 

 rank varies greatly with the naturalist, and the part of the animal kingdom 

 where the group is found. Some families of insects are separated by gaps 

 less than those which divide genera of mammals. 



9 The millepore coral, so abundant in the West Indian Sea, is the work 

 of hydroids. The surface is nearly smooth, with minute punctures. Ge- 

 genbaur, Haeckel, and others hold that the acalephs have no body cavity 

 at all, the internal system of canals being homologous with the intestinal 

 cavity of other animals. 



