10 



HARDWICKE'S SCIEN CE- GOS SIP. 



[Jan. 1, 1S6S. 



deeply embedded in the abdomen, and protected as 

 much as possible from accident. The nettle, on 

 the other hand, is furnished with innumerable 

 stings; but they all lie on the surface of the leaf or 

 stem, exposed to every passing danger, and each in- 

 dividually is weak and fragile. Here then we see 

 the same difference as in the hooks of the bird and 

 the insect. Deprive a wasp of its single sting, it 

 becomes at once a defenceless animal, and must, in 

 the great struggle for existence, inevitably " go 

 under." 



But a nettle may lose ten thousand of its weapons 

 of defence, and yet still show a formidable front to 

 the enemy. In a word, large numbers of compara- 

 tively weak individuals take the place of one or two 

 stout guardians. For of course the hooklets on the 

 insect's wing are intended to answer the same purpose 

 as in the bird. To effect this, the posterior margin 

 of the uppcrwing — in otherwords, the side facing the 

 row of hooklets — is thickened, and folded back suffi- 

 ciently to allow of the hooks having a firm hold when 

 they catch in it. For this purpose no special organ 

 is requisite. The hooks are so situated, that as the 

 animal raises its wings in the effort to fly, they 

 slide over the margin immediately above them 

 without any special effort. And with what result ? 

 Precisely that which we know takes place in the 

 case of the bird. While space is allowed for the air 

 to pass between the wings during the time the 

 latter are being raised, they are held together, and 

 practically become one surface for pressing on the 

 air during the downward stroke. 



The hooklets, as may be supposed, vary greatly 

 both in number and size. In the ants and "such 

 small deer " they are few aud weak. (The ant, be 

 it remembered, wants them but once in its lifetime, 

 and then only for a few hours.) In the huge strong 

 flying hornet there are not less thau a couple of 

 dozen of the stoutest make. 



The aphides being a four- winged family, are also 

 furnished with this remarkable contrivance. Here 

 again they are few and weak, for the aphis is not given 

 to flying: he prefers an easy life on a rose-bush. 

 Moreover, there is a singular variation from the 

 "hooklet" law both of birds and hymenoptera. 

 While in these they are arranged singly along the 

 margin, in the aphides they are collected into a 

 bunch, and appear to emerge as rays from one 

 point. 



Whether this tiny but powerful instrument exists 

 in the other members of the homopterous family — 

 the criads, aphrophorse, &c. — I am not aware ; but 

 that it is in full force in birds and the insects I have 

 mentioned, any experimentalist may ascertain for 

 himself. The wings of a wasp which has died while 

 these organs were firmly clasped together, forms a 

 singularly pleasing object for the microscope, aud one 

 well worth mounting for permanent preservation. 



W. W. Spicer. 



QUEKETT ON HISTOLOGY. 



TTPON inquiry we have learnt that there are 

 ^ many students devoted to the microscope 

 who have never heard that Quekett wrote and pub- 

 lished a work entitled '"'Lectures on Histology." 

 Some who know of its existence have but a crude 

 notion of its contents or objects, and hence consider 

 it of no interest to themselves. As this work is now 

 to be obtained at half its reduced price, or one- 

 fourth its published price, and as every microscopist 

 should be acquainted with it, we hope to render 

 service by explaining what it is, and wherein it con- 

 cerns our readers. 



" Histology is the science of the minute structure 

 of the organs of animals and plants," — so the work 

 commences ; and two volumes of 620 pages are 

 devoted to the description of the microscopic struc- 

 ture of animal and vegetable tissues, illustrated 

 by 423 woodcuts, many of which contain several 

 figures. The first volume is devoted to elementary 

 tissues, and treats of cells and their contents, as 

 well as of vascular tissue and its modifications, 

 fibrous tissues, cartilage, adipose tissue, and pig- 

 ment. The second volume treats of the structure 

 of the skeleton of plants and invertebrate animals, 

 and includes such a wide range of subjects that 

 it would be vain to attempt their enumeration. 

 Sponges, Diatoms, Eoraminifera, Zoophytes, aud 

 Molluscs, all receive attention; aud if the book is 

 only regarded as an illustrated catalogue of Histo- 

 logical objects, it commends itself. But it is more 

 than this, and, despite its faults or failings— for 

 books, like men, are all in this sense imperfect in a 

 greater or less degree— it is a book which deserves 

 to be better known than it is. 

 It would be absurd to write of novelties to be 

 I found in a book published thirteen or fourteen years 

 y ago ; but it is not always the new which is the most 

 j true or the most beautiful. We confess to a liking 

 for the woodcuts, for figures of microscopical 

 objects published in microscopical books are not 

 always either true or beautiful; but some of the 

 figures in this work, although they have been freely 

 copied, have not been surpassed. This is especially 

 the case with hard tissues. It is worthy of note, 

 also, that iu the letterpress the author adheres 

 closely to his subject, does not permit himself to be 

 led away by hypothesis, does not pause to construct 

 theories, does not diverge parenthetically for poetical 

 illustrations, but holds the even tenor of his way, 

 discoursing of what he has observed. 



Now that three hundred students of " the world 

 invisible," by means of the microscope, are united 

 under the name of this author, it would be highly 

 culpable in them not to become acquainted with 

 this, not the least important of his works, especially 

 when it can be accomplished at so small a cost. 



