28 



NA TURE 



\Nov. 9, 1 87 1 



or a gnat or butterfly could be developed from a power- 

 fully mandibulate type like the Orthoptera, or even from 

 the Nruroptera. M. Brauer has recenily sugc^es'ed that 

 the interesting; genus Cainpodca is, of all known existing 

 forms, that which proljably most nearly resembles the 

 parent insect stock. He considers that the grub form of 

 larva is a retrograde type, in which opinion 1 nm unable 

 to concur, though disposed to agree with M. Brauer on 

 the first point. M. Brauer in coming to this conclusion 

 relies partly on geological considerations ; partly on the 

 fact that larva', more or less resembling Cainpodca. are 

 found among widely different groups of insects. 1 think 

 there are other considerations which offer considerable 

 support to this view. No one, so far as I know, has yet 

 attempted to explain, in accordance with Mr. Darwin's 

 views, such a life history as that, for instance, of a butter- 

 fly, in which the mouth is first mandibulate and then 

 suctorial. A clue to the difficulty might, I think, be found 

 in the distinction between developinental and adaptive 

 changes, to which I called the attention of the Society in 

 a previous memoir. The larva: of insects are by no means 

 mere stages in the development of the perfect animal. 

 On the contrary, they are subject to the influence of 

 Natural Selection, and undergo changes which have re- 

 ference entirely to their own requirements and condition. 

 It is evident then that, while the embryonic development 

 of an animal in the egg gives us an epitome of its specific 

 history, this is by no means the case with species in which 

 the immature forms have a separate and independent 

 existence. Hence, if an aniinal when young pursues one 

 mode of life, and lives on one kind of food, and subse- 

 quently, either from its own growth in size and strength, or 

 from any change of season, alters its habits or food, 

 however slightly, immediately it becomes subject to the 

 action of distinct forces ; Natural Selection affects it in 

 two different, and it may be very distinct, manners, 

 gradually leading to differences which may become so 

 great as to involve an intermediate period of change and 

 quiescence. 



There are, however, peculiar difficulties in those cases 

 in which, as among the Lepidoptera. the same species is 

 mandibulate as a larva and suctorial as an imago. From 

 this po'nt of view, however, Cainpodca and the Colh'ni- 

 bpla yPpdiira, &c ) are peculiarly interesting. There are 

 among insects three principal types of mouth, firstly, the 

 mandibulate, secondly, the suctorial, and thirdly, that of 

 Camppdt-a, and the CoUdithola generally, in which the 

 mandibles and ma.xilkv are attached internally, and though 

 far from strong, have some freedom of motion, and can 

 be used for biting and chewing soft substances. This 

 type is intermediate between the other two. /Xssuming 

 that certain representatives of such a type found them- 

 selves in circumstances which made a suctorial mouth 

 advantageous, those individuals would be favoured by 

 Natural Selection in which the mandibles and maxillx 

 were best calculated to pierce or prick, and their power 

 of lateral motion would tend to fall into abeyance, while, 

 on the other hand, if powerful masticatory jaws were an 

 advantage, the opposite process wo'ild tike place. 



There is yet a third possibility — namely, that during the 

 first portion of life the power of mastication should be an 

 advantage, and during the second that of suction, or vice 

 virsA. A certain kind of food might abound at one 

 season and fail at another : might be suitable for the 

 animal at one age and not at another : now in such cases 

 we should have two forces acing successively on each 

 individual, and tending to modify the organisation of the 

 mouth in different directions. It will not be denied that 

 the ten thousand variations in the mouth parts of insects 

 have special reference to the mode of life, and are of some 

 advantage to the species in which they occur. Hence no 

 believer in Natural Selection can doubt the possibility of 

 the three cases above suggested, and the last of which 

 seems to explain the possible origin of species which are 



mandibulate in one period of life and not in another. The 

 change from the one condition to the other would no doubt 

 take place contemporaneously with a change of skin At 

 such times we know that, even when there is no change of 

 form, the temporary softness of the organs often precludes 

 the insect from feeding for a time, as, for instance, is the case 

 in the silkworm. When, however, any considerable change 

 was involved, this period of fasting would be prolonged, 

 and would lead to the existence of a third condition, that of 

 pupa, intermediate between the other two. .Since other 

 changes are more conspicuous than those relating to the 

 mouth, we are apt to associate the pupa state with the 

 acquisition of wings, but the case of the Orthoptera 

 (grasshoppers, &c.) is sufficient proof that the develop- 

 ment of wings is perfectly compatible with continuous 

 activity. So that in reality the necessity for rest is much 

 more intimately connected with the change in the con- 

 stitu'ion of the mouth, although in many cases no doubt 

 the result is accompanied by changes in the legs, and in 

 the internal organisation. It is, however, obvious that a 

 mouth like that of a beetle could not be modified into a 

 suctorial organ like that of a bug or a gnat, because the inter- 

 mediate stages would necessarily be injurious. Neither, 

 on the other hand, for the same reason could the mtjuth 

 of the Hemiptera b^ modified into a mandibulate type 

 like that of the Coleoptera. But in Campodea, and the 

 Collcinbola we have a type of animal closely resembling 

 certain larva: which occur both in the mandibulate and 

 suctorial series of insects, and which possesses a mouth 

 neither distinctly mandibulate nor distinctly suctorial, but 

 constituted on a peculiar type capable of modification in 

 either direction by gradual changes without loss of utility. 

 If these views are correct, the genus Campodea must 

 be regarded as a form of remarkable interest, since it is 

 the living representative of a primaeval type from which 

 not only the Cpllcmbola and Thvsauiir.i but the other 

 great orders of insects have all derived their origin. 



CHARLES BABBACE 

 Died the 2oth of October, 1S71 



THERE is no fear that the worth of the late Charles 

 Babbage will be over-estimated by thisor any gene- 

 ration. To the majority of people he was little known 

 except as an irritable and eccentric person, possessed by 

 a strange idea of a calculating machine, which he failed 

 to carry to completion. Only those who have carefully 

 studied a number of his writings can adequately conceive 

 the nobility of his nature and the depth of his genius. 

 To deny that there were deficiencies in his character, 

 which much diminished the value of his Labours, would be 

 useless, for they were readily apparent in every part of his 

 life. The powers of mind possessed by Mr. Babbage, if 

 used with judgment and persistence upon a limited range 

 of subjects, must have placed him among the few greatest 

 men whocan createnew methods or reform whole branches 

 of knowledge. Unfortunately the works of Babbage are 

 strangely fragmentaiy. It has been stated in the daily 

 press that he wrote eighty volumes ; but most of the eighty 

 pub'ications are short papers, often only a few pages in 

 length, published in the transactions of learned societies. 

 Those to which we can apply the name of books, such as 

 "The Ninth Bridgewater Treatise," ''The Reflections on 

 the Decline of Science," or '' The .Account of the Expo- 

 sition of 1 85 1," are generally incomplete sketches, on which 

 but little care could have been expended. We have, in 

 fact, mere samples of what he could do. He was essen- 

 tially one who began and did not complete. He sowed 

 ideas, the fruit of which has been reaped by men less able 

 but of more thrifty mental habits. 



It was not time that was wanting to him. Born as long 

 ago as the 26th of December, 1792, he has enjoyed a 



