SwiNTON : Physiological Arrangement of Lepidoptera. 99 



to our intent that we should be acquainted with all the scions of the 

 group in question, past and present, any more than it is essential to an 

 artist that every leaf and twig appear in a painting ; for, when links 

 are missing, the shadowy tree of life is not one whit less perfectly 

 indicated by coupling aright those that come under our immediate 

 observation. The simpler the material, the bolder the drawing. 



In the Naturalist for Oct., 1881 (p. 45) I observed that it has been a 

 long standing practice with authors of works on British butterflies to 

 treat the five groups represented in this country in the following 

 order : — Papilionidae, Nymphalid^e, Erycinid^, Lycaenidse, and Hes-' 

 peridse ; but that since the first family, according to Dr. Scudder and 

 others, has close affinity with the last, the method is only plausible on 

 the principle of extremes meeting, the better arrangement every way 

 beiug Nymphalidse, Erycinidae, Lycaenidee, Papilionidae and Hes- 

 peridas. I also added that if physiological reasons could ever be got 

 to prevail over the fancy for having the butterflies first, I would like- 

 wise suggest a further arrangement of the five groups of lepidoptera, 

 showing the development of a structure at the base of the abdomen 

 attributed with the faculty of hearing, that highest of insect senses, 

 thus : N"octuina, Bombycina, Geometrina, Butterflies, and Sphingina. 



Since writing this, a new light has broken upon the subject, and it 

 has become evident to me that the Darwinian tree may be co-ordinated 

 with two lines ; namely, that discovered by Linnseus, in which the 

 mere connexion of the organism being taken into consideration, the 

 branches are thus projected vertically as the shadows fall, and that of 

 more late origin that has taken its rise in the study of structural 

 development, where the branches are projected horizontally, and the 

 degree of perfection of the species is also estimated. The horizontal 

 line of Linnaeus thus sJiows the connexion or the scions in families and 

 genera, the vertical line of the Darwinian school indicates the evolution 

 of races as far as progression is implicated ; and we must believe there 

 has been, on the whole, such progressive development of lepidoptera, 

 although there is not extant sufficient geological, evidence to quarrel 

 about. But whether true in causation as in actuality, that arrange- 

 ment of the groups of the lepidoptera which I have suggested, may be 

 taken as a good outline of the new structural and physiological method 

 which I have previously advocated in my " Insect Variety ; while 

 that worked out with so much pains by Edward Newman, will furnish 

 a good example of the Linncean or horizontal co-ordination. 



I will now show how his latest systematic co-ordination may be 

 projected vertically, and with what result. Instead of the arrangemeDt 



