378 NOTES. 
cation is genealogical; 7. ¢., it is not a mere grouping of like with like, but 
it includes like descent, the cause of similarity. In the existing state of 
science, a perfect classification is impossible, for it involves a perfect knowl- 
edge of all animal structure and life’s history. As it is, it is only a provis- 
ional attempt 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 
language will become more precise and its classification more natural. 
140 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 spe- 
cies, 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. 
141 The Coelenterata and Echinodermata together make up the Radiata, 
the old subkingdom of Cuvier. chinoderma is probably more correct than 
Echinodermata ; but we retain the old orthography. 
142 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. In a philosophical sense, 
Man is a composite being, every organ being an individual, though not an 
independent, existence. An individual repeats the type of its kingdom, sub- 
kingdom, class, order, family, genus, and species, through its whole line of 
descent. 
143 The Millepore coral, so abundant in the West Indian Sea, is the work 
of Hydroids. The surface is nearly smooth, with minute punctures. Ge- 
genbauer, 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. 
1444 Among the exceptions are Tubipora, which have eight tentacles and 
no septa, and the extinct Cyathophylla, whose septa are eight or more. 
145 The longest septa (called primary) are the oldest: the shorter, second- 
ary ones, are developed afterward. As a rule, sclerodermic corals are cal- 
careous, and a section is star-like; the sclerobasic are horny and solid. 
The latter are considered higher in rank. 
146 Some Star-fishes (Solaster) have twelve rays. In all Echinoderms, prob- 
ably, sea-water is freely admitted into the body-cavity around the viscera. 
The canals likewise contain water, which enters through a porous tubercle, 
the madreporiform plate, or ‘dorsal wart,” best seen on the back of the Star- 
fish and Sea-urchin.—By some, Echinoderms are regarded as Worms. 
147 The shell is not strictly external, like the crust of a Lobster, but is 
coated with the soft substance of the animal. 
148 Six hundred pieces have been counted in the shell alone, and twelve 
hundred spines. The feet number about three thousand. They can be pro- 
truded beyond the longest spines. 
149 The most important genera are Terebratula, Rhynchonella, Discina, Lin- 
gula, Orthis, Spirifer, and Productus. The first four have representatives in 
existing seas. Professor Morse, indorsed by Kowalensky, maintains the 
