It is quite possible that the characters of the nematocysts might afford data as useful to the systematist in this group as do the spicules of sponges, for instance.
Premising then that the chief characters assigned by this systematist to his several groups are drawn from almost all parts of the structure of birds, and are supplemented by some others of their more prominent peculiarities, we present the following abstract of his scheme:-2 I.
Moreover, as Professor Burmeister states in his preface, Nitzsch by no means regarded the natural sequence of groups as the highest problem of the systematist, but rather their correct limitation.
Herein he divided the class A y es into two subclasses, to which he applied the names of Insessores and Grallatores (hitherto used by their inventors Vigors and Illiger in a different sense), in the latter work relying chiefly for this division on characters which had not before been used by any systematist, namely that in the former group monogamy generally prevailed and the helpless nestlings were fed by their parents, while the latter group were mostly polygamous, and the chicks at birth were active and capable of feeding themselves.
Physiology may one day very likely assist the systematist; but it must be real physiology and not a sham.
Thus he separates the birds of prey into three great groups - (I) the ordinary Diurnal forms, including the Falconidae and Vulturidae of the systematist of his time; but distinguishing the American Vultures from those of the Old World; (2) Gypogeranus, the secretary-bird; and (3) the owls (q.v.).
It is enough to point out that we have in his work another proof of the multiplicity of the factors which must be taken into consideration by the systematist, and another proof of the fallacy of trusting to one set of characters alone.
The early collectors of natural curiosities were the founders of zoological science, and to this day the naturalisttraveller and his correlative, the museum curator and systematist, play a most important part in the progress of zoology.
The subject-matter of this new science, or branch of biological science, had been neglected: it did not form part of the studies of the collector and systematist, nor was it a branch of anatomy, nor of the physiology pursued by medical men, nor again was it included in the field of microscopy and the celltheory.
Thus not only did Darwin's theory give a new basis to the study of organic 'structure, but, whilst rendering the general theory of organic evolution equally acceptable and Effects of necessary, it explained the existence of low and simple forms of life as survivals of the earliest ancestry of theory more highly complex forms, and revealed the classifications of the systematist as unconscious attempts to construct the genealogical tree or pedigree of plants and animals.
- The work of the collector and systematist: exemplified by Linnaeus and his predecessors, by Cuvier, Agassiz, Haeckel.
The actual boundaries between animals and plants are artificial; they are rather due to the ingenious analysis of the systematist than actually resident in objective nature.
The determination of the course of descent has now become the ultimate problem for the systematist: this is an historical question, and the historical documents available are the remains of the ancient organisms preserved in the rocks.
The German systematist, A.
Poulton, in an admirable discussion of contemporary views regarding species (presidential address to the Entomological Society of London 1904), has shown that Darwin did not believe in the objective existence of species, not only because he was led to discard the hypothesis of special creation as the explanation of the polymorphism of life, but because in practice as a working systematist he could neither find for himself nor ascertain from other systematists any settled criteria by which a group of specimens could be elevated into a genus, accepted as a species, or regarded as a variety.