4440 THE ZooLocist—May, 1875. 
1835, in introducing one of my earliest lucubrations to the public, 
I ventured to submit what most of my fellow-labourers thought 
the crude and ill-considered opinion that “ Introductory works on 
science should be written for those who know nothing of the 
subject on which they read, and by those who possess in them- 
selves some practical knowledge of the subject on which they 
write.” It will be observed by any one who opens Professor 
Newton’s ‘Zoology’ that he and I are opposed on the first moiety 
of this proposition, since he appears to be unaware of the possible 
existence of ignorance in Zoology, and to write for our teachers as 
much as for ourselves: he soars above all our heads; at least it is 
so with me; for when I have read the whole, including the 
explanatory summary with which he concludes, and which I have 
cited below, I pause a moment to take breath, and then exclaim, 
“How wonderful! What a display of learning! but it cannot be 
intended for the likes of me.” 
“Should we wish to express more clearly how this common bond of life 
unites the whole animal world, we cannot do better than by adopting the 
form of a genealogical tree with the various branches, nearly as it has been 
drawn by Professor Allman {in his Address delivered to the Biological 
Section of the British Association at Bradford, 1873, p. 5]. 
“ Starting from the Protozoa as the root, we are led on one side through 
the Rhizopods to the Hydra-like animals of the group Ccelenterata, and there 
that line soon comes to an end; but from the Infusores, which may be 
regarded as on a level with the Rhizopods, we pass to the lowest group of 
the Vermes, namely, the Helminthes, and thence to the Annelids, or highest. 
Here we find our tree sending forth three branches, two of which, the 
Echinodermata and Arthropoda, are connected with the stock by the 
Star-fishes and Crustaceans respectively, while the third, the “Polyzoa, 
shoots upwards to the Tunicates, the highest group of the Molluscoidea. 
Thence again arise two branches, one not extending very far, and ending 
in the Mollusca, while the other points to the Lancelet (Branchiostoma), 
the lowest member of the great group Vertebrata. Arrived there the 
general sequence, as it has already been given in this book, is plain, and 
the series of creatures culminates in Man.”—P. 127. 
I have never seen any reason to doubt, first, that the Vertebrata, 
or more properly “ Endosteata,” are the central group of the animal 
kingdom, the others being the Exosteates (or Articulates), the 
Anosteates (or Mollusks) and the Actiniates (or Radiates); secondly, 
that the sucklers are the central group of Endosteates, the other 
Th i ak est 
