4o8 



NA TURE 



[Mar. 26, 1874 



relations to spacg, and that the order, as a whole, is, as far 

 as yet known, remarkably restricted as regards geological 



The comparisons instituted in our survey of the frog's 

 anatomy will enable us now to sum up resemblances ; 

 first, as regards the orders of its class, and secondly, as 

 regards the class itself. 



1. Its own order, Aiioiwa, has been seen to present 

 singular resemblances to the Chelonia amongst reptiles. 

 Such are the bony plates of the back of some forms, the 

 bony covering of the temporal fossa in others, the mode of 

 inspiration in the adult, the armature of the jaws in the 

 young. On the other hard, the peculiar elongated tarsus has 

 reminded us of certain mammals, and the median Eusta- 

 chian opening of Pipa and DactyhtJira has suggested an 

 affinity to crocodiles and birds. It has been plain, how- 

 ever, that these several likenesses, however singular and 

 striking, are not evidences of genetic affinity. 



2. The order Urodcla may well recall to mind the 

 Lacertilia amongst reptiles, with which animals the Uroacla 

 were actually classed by Linneus. Moreover in both 

 groups we find a series of different species, longer and 

 longer in body and shorter and shorter in hmb. We 

 have also seen that in both these groups an analogous 

 complication obtains in the muscles of the legs. 



3. The order Upliioniorplia, as has been before observed, 

 present a general resemblance to serpents, and a special 

 resemblance to certain short-tailed ones ; though it is 

 rather 10 the Amphisbenian Saurians that they may most 

 advantageously be compared. Here, again, however, we 

 meet with the resemblances which, though striking, do 

 not allow themselves to be interpreted as indices of any 

 special relationship by descent. 



4. The order Labyriiitliodoiita recalls to mind, as has 

 been said earlier, the Crocodilia amongst reptiles, of which 

 they may be deemed as the prophetic precursors, so to 

 speak, though certainly not the direct ancestors. 



Thus the class Batracliia, as a whole, presents a very 

 interesting analogy and parallelism with the class Repiilia. 

 It is a parallelism, moreover, which reminds us of that 

 which exists between the various orders of Placental mam- 

 mals and the great subdivisions of the pouched or Marsu- 

 pial order of mammals. We have carnivorous, insectivorous, 

 arboreal, aquatic, herbivorous, marsupial beasts, as we 

 have carnivorous, insectivorous, arboreal, aquatic and her- 

 bivorous placental beasts. The harmonious variations of 

 the placental and marsupial groups thus present us with 

 excellent instances of affinities independently evolved and 

 not due to hereditary infiuence. 



In a similar way it seems probable that the subdivisions 

 (orders) of the class IJatrachia, mimic, as it were quite 

 independently, the subdivisions (orders) of the class Reptilia. 



The Frogs' class, as a whole, shows as many striking 

 affinities to some or other fishes. It does so in the pos- 

 session of gills and of a branchial apparatus during one 

 time of life at the least ; a large parasphcnoid in the skull; 

 the often persistently unsegmented terminal part of the 

 notochord ; the single ventricular cavity ot the heart ; the 

 presence of a hulhiis aorta ; the development of a Jicrvus 

 lateralis ; the communication between the urinary canal 

 and the oviduct, and certain other characters of less im- 

 portance. 



The class Batrachia agrees both with fishes and reptiles 

 in having the blood cold, more than one aortic arch, and 

 (e.\cept in crocodiles) in not having the distinct ventricles. 



The class agrees with fishes, reptiles, and birds, in hav- 

 ing no complete diaphragm, and no corpus callosum* in 

 the brain, and no single aorta arching over the left bronchus. 



We have now arrived at the end of those considerations 

 seemingly best suited to enable us to answer the initial 

 question, " What is a Frog ? " The requisite definition 

 might, of course, have been given much earlier, but these 

 inquiries have seemed necessary to enable the reader to 



* As to this structure see Lesson in " Elementary Anatomy," pp. 367, 375. 



understand the technical terms of such definition — to give 

 them, in his eyes, a real meaning. 



The Frog is a tailless, lung-breathing, branchiate verte- 

 brate, with four limbs typically differentiated, undergoing a 

 complete metamorphosis, and provided with teeth along 

 margins of the upper jaw. 



The course of our inquiry into the nature and affinities 

 of the Frog has not alone sen ed to answer the question 

 with which this memoir opened. Incidental bearings upon 

 deep biological problems have come before us more than 

 once in its course, nor have all the conclusions which seem 

 to have forced themselves upon us been totally negative. 



Thus we have met with several instances of the inde- 

 pendent origin of remarkably similar structures, such as 

 a shielded temporal fossa and elongated tarsus, which, 

 together with structures like the tooth of the Labyrintho- 

 don, seem to be characters for the existence of which 

 neither the destructive agencies of nature acting on minute 

 oscillations of structure, nor any sexual phenomena, will 

 account. 



Again, in the life-history of the Frog, considered even 

 purely by itself, we find a remarkable example of sponta- 

 neous transformations due to innate powers and tendencies. 



When, however, this process is considered in the light 

 derived from the curious phenomena of transformation so 

 enigmatically presented to us by the axolotl, we have very 

 strongly brought before us the powerful action of internal 

 tendencies lying dormant and latent till made manifest, 

 through the advent of conditions so obscure that as yet 

 they have evaded the most careful and anxious scrutiny 

 of practiced adepts. 



It would seem to be a negligence not here to point out, 

 that if new forms of life— new species — arise from time to 

 time through congenital variation, not a few of the facts 

 herein quoted point to the probability that such forms 

 have arisen through the evolutions of implanted potentia- 

 lities definite in nature, in other words, by " specific 

 genesis." 



Again, a general survey of the different kinds of relations 

 which the Frog has brough'. before us, is well calculated to 

 impress us with the overwhelming richness and fulness of 

 nature. 



Although, from our ignorance, the natural history of 

 many other animals well known to us may appear less 

 replete with interest than that of the common Frog may 

 now be, yet it cannot be doubted but that the progress of 

 science is capable of revealing to us facts as full of in- 

 struction and of as profound a significance in the life his- 

 tory of almost any kind of animal whatever. 



Ever fresh, ever fertile, natural history offers to our 

 faculties a pursuit practically inexhaustible. We are not, 

 indeed, denied the gratification of successfully exploring 

 and satisfactorily explaining mystery after mystery, but 

 each secret wrested by our efforts brings before us other 

 ever new enigmas, so that though refreshed by success we 

 need never be wearied by monotony. While we need not 

 regard any problem as absolutely hopeless, no dread of 

 coming to the end of our inquiries need ever chill the 

 warmth of our zeal in the scientific cause. Some may 

 consider such reflections justified by the phenomena pre- 

 sented to them by the natural history of the Common 

 Frog. 



St. George Mivart 



THE HABITS OF BEES AND WASPS* 



SIR JOHN LUBBOCK, in a paper on the Social 

 Hymenoptera (Bees, Wasps, and Ants), especially 

 with reference to their habits, senses, and power of com- 

 munication with one another, pointed out with regard to 

 the latter, that the observations on record scarcely justify 

 the conclusions which have been drawn from them. 



* Being the substance of a paper by Sir John Lubbock, Kart.. F.R. Sp- 

 read before the Linnean Society on the 19th March, 1874. 



