SCIENCE. 



[Vol. XXII. No. 558 



house-flies and their allies, together with the sheeptick 

 (Pupipara) as being the most highly modified, and the 

 last to appear, of the dipterous series. 



In the Hj'menoptera there is nothing of this kind, we do 

 not have entire groups of this order which have become 

 so reduced, degenerate and modified, largely the result of 

 parasitic life, as in the flies. The Hymenoptera are a 

 normal blossoming or branching out of the topmost por- 

 tion of the tree of insect life, while we should regard the 

 Diptera as a degenerate, retrograde, downfallen branch. 



If we look at the larvpe of Diptera we shall see that the 

 most perfectly developed or highly differentiated forms 

 are those of mosquitoes, black flies and the Tipulidfe, etc., 

 (Encephala); then we pass on to a series in which the 

 body becomes more and more maggot-like, the head be- 

 ing so reduced in the Muscidfe (in the old sense) that it 

 is difficult to make out the homologies of the antennae 

 and parts of the mouth. The internal organs, as the 

 tracheae, share in this alteration and extreme modification 

 of parts' adapting the maggot for its parasitic or other- 

 wise peculiar mode of life and surroundings. Indeed, be- 

 low the families embraced in the Orthorapha (Culicidfe, 

 Simuiidfe, etc.), the great group of Diptera now consists 

 of very degenerate, highly modified forms. 



Now under what canons of taxonomy are we to act in 

 considering what forms are "high" and what are "low," un- 

 less we take into account the facts we have considered ? 

 It seems to us that the few entomologists and other nat- 

 uralists who advocate placing the Diptera at the head of 

 the insect series, disregard the fact that the processes of 

 degeneration, reduction, with specialization in limited 

 directions, and of adaptation to unusual modes of life, 

 their habits being, in many groups, parasitic, or partially 

 so, have brought about a modification of larval and adult 

 structure, such as we do not find in any of the other larger 

 orders of insects. 



It seems to savor somewhat of a violation of the princi- 

 ples of classification, which in these days is based not 

 only on comparative anatomy, but on mori^hology, 

 paleontological history, and the facts of adaijtation to 

 changed conditions of existence, to give the highest rank 

 to a group in which disuse of certain parts leading 

 to degeneration, and the modification of other parts 

 adapting them for quite peculiar uses, are so marked. 

 And it is this wonderful amount and variety of modifica- 

 tion and adaptation to this or that mode of life which 

 makes the group one of such striking interest to the phil- 

 osophic student. We see how much at the mercy of the 

 environment the group has been exposed, and this is 

 especially striking when we compare the Diptera with the 

 great group of Lepidoptera, where there is a striking per- 

 sistence and fixity of structural features, both in larva 

 and imago, as well as in the modes of life, and the nature 

 of the food. 



BOOK-EEVIEWS. 



British Locomotives, their History, Construction and Modern 

 Development. By C J. Cooke. Whittaker & Co., Lon- 

 don and New York, 1893. 376 p. 12mo. $2.00. 

 An interesting and very instructive account of the rise 

 and progress of the locomotive, especially in Great Brit- 

 ain, including important details of construction and 

 dimensions, as well as performance. It is written in a 

 sufficiently popular style to be readable by any one hav- 

 ing an interest in its subject, and is yet sufficiently tech- 

 nical to satisfy the specialist desiring information in rela- 

 tion to the proportions and the work, or even the general 

 plans, of locomotives, old and new, including, of course, 

 the now familiar "compound engine." The book is ad- 

 dressed, and most suitably, to all who take an intelligent 



interest in the working of the locomotive and of railways' 

 and to practical railway mechanics as well. It is written 

 by an employe of the London and Northwestern Railway, 

 and is therefore reliable and accurate; its illustrations are 

 from working drawings, and are supplied by the great 

 locomotive designers of the United Kingdom, and are, 

 therefore, valuable to the professional, as w-ell as useful 

 to the casual, reader. The early history of the engine, of 

 the struggles in which George Stephenson and his con- 

 temporaries engaged to make steam a successful railway 

 motor, and the later account of the modern compound en- 

 gine are likely to prove most interesting to the average 

 reader; but no one should omit the careful perusal of the 

 last chapter, on the duties of the locomotive engine- 

 driver, in which he will find much to impress him with 

 the wonderful combination of courage, skill, intelligence, 

 foresight, knowledge and readiness, in times of emergency, 

 which is demanded of that humble and rarely appreciated 

 craftsman. 

 Negative Beneficence and Positive Beneficence : Being Parts 



V and VI of the Principles of Ethics. By Heebeet Spencer. 



New York, D. Appleton & Co. 12mo. $1.25. 



This volume comjiletes Mr. Spencer's ethical treatise, so 

 that all who wish to know the final views of the philoso- 

 pher of evolution on questions of conduct and duty are 

 now enabled to do so. In the opening chapter Mr. Spen- 

 cer draws a very sharp distinction betw'een beneficence 

 and justice, as he understands these terms, and then pro- 

 ceeds to show that beneficence has two forms, the positive 

 and the negative. He then discusses various forms of 

 negative beneficence, which consist in refraining from 

 acts that woxdd be injurious to others or to society at 

 large, and afterwards those forms of positive beneficence 

 which he deems most important. He confines himself al- 

 most entirely to private and industrial life, and we look 

 in vain in these pages for any recognition of that benefi- 

 cence that shows itself in advancing human knowledge 

 and human virtue. Indeed, with the exception of certain 

 passages in which the author's excessive individualism 

 shows itself, the book is of a commonplace character; and 

 whoever takes it up with the expectation of having his 

 moral ideas clarified or his moral sentiments quickened 

 and elevated, will be disappointed. 



But what is more remarkable is that Mr. Spencer, as 

 we learn from his preface, is himself disappointed; for, 

 after congratulating himself on the completion of the 

 work, he says: 



"My satisfaction is somewhat dashed by the thought 

 that these new parts fall short of expectation. The doc- 

 trine of evolution has not furnished guidance to the ex- 

 tent I had hoped. Most of the conclusions drawn empir- 

 ically, are such as right feelings, enlightened by culti- 

 vated intelligence, have already sufficed to establish. Be- 

 yond certain general sanctions indirectly referred to in 

 the verification, there are only here and there, and more 

 especially in the closing chapters, conclusions evolution- 

 ary in origin that are additional to, or different from, 

 those which are current. ' For our part, we can see no 

 connection between the law of evolution as propounded 

 by Mr. Spencer and the moral law; and we cannot per- 

 ceive that he has shown the existence of such a connec- 

 tion. Both in this volume and in the preceding one on 

 "Justice" evoliitionar3- jDrinciples are brought in only oc- 

 casionally and incidentally; and, when they are brought 

 in, they are generally irrelevant to the discussion. In- 

 deed, how can the studj' of a merely natural jsrocess like 

 evolution teach us what we ought to do '? How can we 

 even know whether evolution itself makes for good or 

 for ill unless we already have a moral ideal by which to 

 judge its results ? We fear that those who have been 

 expecting evolutionism to furnish a guide of life will have 

 to look in some other direction. 



