PART 11. PRINCIPLES OF MORPHOGENESIS OR EVOLUTION 



OF FORM 



NEED OF TAXONOMY 



W. T. Caiman, keeper of zoology in the British Museum of Natural History, says in his recent 

 address, "The Taxonomic Outlook in Zoology,"^ that in the days of Linnasus (1758) an experi- 

 enced zoologist might have known the 4370 living species then named, but that to-day, when over 

 700,000 kinds have been described, the great need for the specialist is apparent. "Nothing can alto- 

 gether replace that instinctive perception of affinity that comes from lifelong study" (p. 280). He 

 goes on to say, however, that there can no longer be a "complete description" of a species, as was 

 thought necessary by the older systematists, but that what should be done is to enumerate the essen- 

 tial characters in which it differs from similar forms of the genus. This address stimulated the 

 editor of Nature to remark:" "There is a strong tendency to deprecate the value of taxonomy and 

 to ignore its claims to a fair share of the attentions of scientific workers." 



All animal life is subject to change as soon as the normal conditions of the environment change, 

 and, according to Baker,^ "there is evidence that this change may not always be a matter of long years 

 but may take place in the space of five or ten years. This statement is abundantly supported by 

 experimental evidence. The necessity for giving names to these incipient species [ecological variants] 

 is, therefore, obvious." 



The same writer has shown elsewhere that molluscs in streams and lakes change into different 

 forms in the course of one or two human generations, due to alterations in the environment brought 

 about by man. If subspecies change thus quickly, paleontologists with their superabundance of time 

 as recorded in the geological formations must expect generic change from zone to zone, and yet no 

 genus should be made on the basis of age alone, since a genus is to be founded on the ensemble of 

 characters as seen in one or more species. 



It is said that Linnsus described in the tenth edition of his "Systema Naturae" (1758) one 

 genus and forty-two species of Homoptera. Now Professor Z. P. Metcalf, a student of this "small 

 order of insects," estimates that there are known no fewer than 30,000 species distributed in 500 

 genera, and it is thought that there will eventually be three times as many. In this group, therefore, 

 and in many others, it is only too plain that there can be no stability in nomenclature for a long time 

 to come. It does not further our subject, however, to complain of the multiplicity of Nature and the 

 consequent difficulties in attempting to give the proper name to each species under the Rules of 

 Zoological Nomenclature. It is the duty of every systematist to do the best he can and let the future 

 take care of itself. In other words, the grumblings of the anatomists, physiologists, experimental 

 biologists, etc., are all beside the mark, since the systematist is only trying to classify what he sees in 

 an ever changing world, namely, to determine the lines of organic descent to the uttermost ramifica- 

 tions possible in a stated classification that is, after all, more or less artificial. Morphology will 

 grow and taxonomy will change as long as there are great numbers of unknown species and genera. 



RISE OF BRACHIOPOD GENERA 



Fabius Columna in 1616, and Martin Lister in 1678, were the first to describe brachiopods, 

 calling them Conchie anomice. Grundler in 1774 was the first to give a good illustration of a living 

 brachiopod, TerebratuUna cafut-serfentis. Cuvier in 1792 and 1802 distinguished brachiopods from 

 Acephala, and in 1805 gave the class its name Brachiopoda. In 1818 Lamarck knew 5 genera, 



^Science, n. ser., vol. 72, 1930, pp. 280-284; Nature, vol. 126, 1930, pp. 440-444. 



-Nature, vol. 126, 1930, pp. 461-462. 



^ F. C. Baker, On Genus and Species Making. Science, n. ser,, vol. 72, 1930, pp. 37-39. 



