Oct. 28, 1875] 



NATURE 



553 



OUR BOOK SHELF 



Zoology for Students. By C. Carter Blake, D.Sc. 

 (Daldy, Isbister, and Co., 1875.) 



In this work Dr. C. C, Blake has published, as he tells 

 us in the preface, the substance of his annual course of 

 lectures on zoology at Westminster Hospital. Beginning 

 with the highest form, man, he descends the whole scale of 

 animal life, ending with the Protozoa, or Acrita. A general 

 description of each class is followed by a more detailed 

 account of each of the different orders which compose it. 

 As a preface, " notes " taken from some of Prof. 

 Owen's Hunterian Lectures on the principles of zoo- 

 logical classification, are, with the lecturer's permission, 

 introduced. 



The arrangement adopted is not the most modern. The 

 Batrachinaand the other Amphibia are retained as orders 

 of the class Reptilia ; the importance of the different sec- 

 tions of the Teleostei is considered to be as great as that 

 of the Ganoidei or Plagiostcmi ; the Cirripedia are sepa- 

 rated from the Crustacea; the " Bryozoa" are asso- 

 ciated with the " Radiata," and the Entozoa are retained 

 among the Articulata. More stress is laid on external 

 peculiarities than is the custom now-a-days, among bio- 

 logists, and the importance of embryology is not made 

 prominent. Theoretical considerations are placed in the 

 background, and illustrations are but few and far between. 

 The fossil orders are described in their respective classes, 

 and some of Prof. Owen's tables of the distribution in 

 time of their different genera are introduced. 



There is, no doubt, some advantage to a student with 

 time at his disposal commencing the science upon an 

 antiquated classification, for it enables him afterwards 

 to more fully comprehend the history of biology, and to 

 appreciate the rapid strides that have been made. We, 

 however, fear that it is the object of most who take up the 

 subject to obtain, as quickly as possible, a clear idea 

 of its present position ; and such being the case, to com- 

 mence with a bygone system is only so much loss of 

 time. The view taken by Dr. Blake will therefore detract 

 from the value of his otherwise useful work. Another thing 

 that will diminish its value is a certain want of accuracy 

 which pervades it. Drawings of the feet of three birds 

 are given, and they are all wrongly named. A scansorial 

 foot is adjudged to a passerine bird ; that of a kingfisher 

 is said to be gallinaceous, whilst that of a steganopod is 

 termed " foot of duck." More than once the peculiarities 

 of two closely allied animals are reversed, as when we are 

 told that among the Proboscidia " in one form, entirely 

 extinct (Dinotherium), the incisors project in the form of 

 long tusks from the upper jaw ; in the existing elephants, 

 from the lower jaw," and when " the articulated group (of 

 the Brachiopoda are said to) possess an anal aperture, 

 the non-articulated possess none whatever." 



The chapter on the Pisces is much confused. " The 

 living Ganoids have completely bony skeletons, but the 

 fossil ones may have had skeletons soft and cartilaginous 

 like those of the Sturgeons. . . . They have several 

 holes in the arterial trunks. . . . Their optic nerves do 

 not decussate, but merely cohere laterally." The external 

 pares are said to be "simple" in the Rays and Sharks, 

 or *' double, as in most osseous fishes." The Ammocete 

 is called the Sandlaunce, and it is described as a separate 

 genus. 



The same character is more than once repeated on the 

 same or the following page, whilst others equally important 

 are omitted. On the first page of the section describing 

 the Reptilia, the two following sentences occur as parts of 

 the definition of the class : " a heart with two auricles, and 

 with the ventricle more or less completely divided ; " 

 " the heart has two auricles ; the ventricle is imperfectly 

 divided." Pentastoma is retained among the " Entozoa," 

 instead of being placed among the Arachnida ; we can 

 find no reference to Ceratodus, a most important fish 



theoretically ; and the brain of the Marsupials is said not 

 to possess a corpus callosum. 



Notwithstanding the imperfections above pointed out, 

 there is much to be learnt from Dr. Blake's work ; many 

 of the descriptions are excellent ; nevertheless there are 

 so many essential facts omitted, that it will be found more 

 valuable as an adjunct to a work like Prof. Huxley's 

 " Introduction to the Classification of Animals," than as 

 an independent source of information. 



LETTERS TO THE EDITOR 



[The Editor does not kold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 ■No notice is taken of anonymous covimunicatiotis.\ 

 " Instinct and Acquisition " 



In Nature (vol. xii. p. 507) there appears, under the above 

 heading, a very interesting article, being an epitome of a paper 

 read by Mr. Spalding at the Bristol meeting of the British Asso- 

 ciation. Now that the doctrine which is maintained in this 

 article — a doctrine with which Mr. Spalding's name is associated 

 as almost its only experimental verifier — has proved itself so 

 completely victorious in overcoming the counter-doctrine of 

 "the individual-experience psychology" — and this along the 

 whole line both of fact and theory — it seems unnecessary for 

 anyone to adduce additional facts in confirmation of the views 

 which Mr. Spalding advocates. I shall therefore confine myself 

 to detailing a few results yielded by experiments which were 

 designed to illustrate the subordinate doctrine thus alluded to in 

 Mr. Spalding's article : — 



" Though the instincts of animals appear and disappear in 

 such seasonable correspondence with their own wants and the 

 wants of their offspring as to be a slanding subject of wonder, 

 they have by no means the fixed and unalterable character by 

 which some would distinguish them from the higher faculties of 

 the human race. They vary in the individuals as does 

 their physical structure. Animals can learn what they did 

 not know by instinct and forget the instinctive knowledge 

 which they never learned, while their instincts will often 

 accommodate themselves to considerable changes in the order of 

 external events. Everybody knows it to be a common practice 

 to hatch ducks' eggs under a common hen, though in such cases 

 the hen has to sit a week longer than on her own eggs. I tried 

 an experiment to ascertain how far the time of sitting could be 

 interfered with in the opposite direction. Two hens became 

 broody on the same day, and I set them on dummies. On the 

 third day I put two chicks a day old to one of the hens. She 

 pecked at them once or twice, seemed rather fidgety, then took 

 to them, called them to her, and entered on all the cares of 

 a mother. The other hen was similarly tried, but with a very 

 different result. She pecked at the chickens viciously, and both 

 that day and the next stubbornly refused to have anything to do 

 with them," &c. 



It would have been well if Mr. Spalding had stated whether 

 these two hens belonged to the same breed ; for, as is of 

 course well known, different breeds exhibit great variations in 

 the character of the incubatory instinct. Here, for instance, is a 

 curious case. Spanish hens, as is notorious, scarcely ever sit at 

 all; but I have one purely-bred one just now that sat on dummies 

 for three days, after which time her patience became exhausted. 

 However, she seemed to think that the self-sacrifice she had 

 undergone during these three days merited some reward, for, on 

 leaving the nest, she turned foster-mother to all the Spanish 

 chickens in the yard. These were sixteen in number, and of all 

 ages, from that at which their own mothers had just left them up 

 to full-grown chickens. It is remarkable, too, that although 

 there were Brahma and Hamburg chickens in the same yard, 

 the Spanish hen only adopted those that were of her own breed. 

 It is now four weeks since this adoption took place, but the 

 mother as yet shows no ; igns of wi-shing to cast off her hetero- 

 geneous brood, notwithstanding some of her adopted chickens 

 have grown nearly as large as herself. 



The following, however, is a better example of what may be 

 called plasticity of instinct. Three years ago I gave a pea-fowl's 

 egg to a Brahma hen to hatch. The hen was an old one, and 

 had previously reared many broods of ordinary chickens with 

 unusual success even for one of her breed. In order to hatch the 



