March 31, 1887] 



NA TURE 



511 



by the agency of small animals quoted as if they were 

 \vell-e;tablished facts (p. 184). Chara is spoken of as "a 

 sort of transition stage " between the red and brown sea- 

 weeds (p. 1991. We fail to find any grounds for this 

 extraordinary statement. We are informed that in 

 Selaginella " the rain or dew will settle in the hollow 

 of the leaf, and help to float the zoosperms ; but in Pinus 

 their dry and motionless representatives are more exposed 

 to the wind on the outer surface of the leaf" (p. 279). It 

 would be difficult to frame a sentence more hopelessly 

 inaccurate than this. 



The following passage from the introductory chapter is 

 worth quoting: "Morphology by itself is thus seen to 

 be a matter of mechanism, revealing nothing higher than 

 a combination of mechanical movements, harmonious in 

 action and beautiful in execution ; but physiology, depend- 

 ent on structure for the interpretation of the phenomena 

 of life and the causes thereof, seeks to reveal the inner 

 life as well as the outward expression of it " (p. 10). It 

 will probably be new to most of us to Icarn that morpho- 

 logy reveals movements at all, mechanical or otherwise. 



At p. 179 "apogamy " and " self-fertilisation " are used 

 as equivalent terms ; at p. 138 Spirogyra is said to produce 

 gonidia, and at p. 25 reproduction in Selaginella is said 

 to take place by means of a true seed. 



We have only cited a few examples of positive errors, 

 but throughout the book the terminology is strange and 

 confusing, even where not absolutely incorrect. 



The book is presumably intended for students " cram- 

 ming ' for examinations, but even for this purpose we 

 fear that it will prove worse than useless. D. H. S. 



LETTERS TO THE EDITOR 



[Tii Elti)r Joes not hold himself responsible for opinionsex- 

 pressed by his correspondents. Neither can he undertake to 

 return. Of- to correspond with the writers of, rejected manu- 

 scripts. No notice is taken of anonymous communications . 



( The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts. ] 



Vitality, and its Definition 



It is perh.ips desirable that I should offer a few words of 

 explanation, by w.iy of reply to several of your correspondents, 

 who have con-mented upon certain statements in my recent 

 address to the Geological .Society. 



In the first place, I think that any candid reader of that address 

 will acquit me of being guilty of such presumption .is to make a 

 statement, on my own authority, concerning the vitality of 

 seeds. My object was to contrast the greater stability of mineral 

 structures with the lesser stability of animal and vegetable 

 structures. Consequently I selected what I thought would be 

 regarded as the extreme examples of prolonged vitality in the 

 animal and vegetable worlds respectively. It was quite sufficient 

 for my purpose that competent botanists have cited the case of 

 the germination of seeds taken from ancient Egyptian tombs as 

 authentic, and that a botanist of such eminence as A. de Candolle 

 should assure us that it is "not impossible." .\s a matter of 

 fact, I have been informed, however, by a reliable authority that 

 experiments on the germination of seeds taken from mummies 

 have very recently been conducted to a successful issue. 



With respect to Mr. Herbert Spencer's definition of life, my 

 object was not to find fault with it but to show that the ditTer- 

 ences between "organic" and "inorganic" matter are of so 

 shadowy a kind as to defy definition. Even straining the mean- 

 ing of the word "correspondence" so as to give it the force 

 implied in the pass.ige cited from the " Principles of Biology " 

 by your correspondent Mr. Collins, I maintain th.it in those 

 changes undergone by minerals to which I apply the term 

 "physiological" there is a complete "correspondence with 

 external sequences." When the temperature of a crystal is 

 altered through a certain range, expansion and contraction take 

 place unequally in accordance with the molecular structure of 

 the mass. In consequence of this unequal expansion and con- 



traction, stresses are produced and the crystal undergoes an 

 internal molecular rearrangement, which is determined by a 

 latent "organisation," though it can only be detected, perhaps, 

 by its action on the light-waves. Kut now let another set of 

 forces come into play, namely, the chemical action of liquids 

 containing gases in solution, and immediately the effects of the 

 former change are seen in the manner in which the crystal yields 

 to the new forces operating upon it. This secondary change is in 

 fact only rendered possible by the primary one having taken place. 

 Hut the changes produced by solvent action in turn weaken the 

 stability of the whole mass, permitting other chemical affinities 

 to assert themselves, in consequence of which the crystal enters 

 upon a long series of metamorphoses which terminate in the 

 complete " dissolution " of the ties that held together its 

 molecules ; it thus becomes a pseudomorph, a sort of mineral 

 corpse, with the external form of the original crystal only, but 

 without any of that capacity for undergoing a wonderful cycle of 

 changes which was its original endowment. After this the 

 materials of the "dead" crystal may be used up to form the 

 substance of new ones. 



It is scarcely necessai^ to add that I had no serious intention of 

 asserting that minerals do actu.ally live, in the sense in which 

 "living" is popularly understood. All I care to insist upon is 

 that minerals, like animals and plants, go through definite cycles 

 of change, dependent on their environment, and that the dis- 

 tinction between " organic " or "living "matter and "inorganic" 

 or " lifeless " matter is therefore not a fundamental one. Surely 

 no better proof of this can be adduced than the fact that the 

 more exact we try to make our definitions of the terms " life " 

 and "organisation," the more shadowy and intangible become 

 the distinctions upon which we are driven to depend. I am 

 perfectly satisfied with Mr. Herbert Spencer's admission of 

 " insensible modifications and gradual transitions which render 

 definition impossible." But if this be the case, it is surely not 

 wise to maintain that the science of " non-living " beings must 

 differ totally in its aims and its methods from that of " living" 

 beings. To bring out into cle.ar relief the analogies between the 

 science dealing with the mineral kingdom and those concerned 

 with the animal and vegetable kingdoms was the main object 

 of my address. John W. Judd 



March 28 



" The Gecko moves its Upper Jaw " 

 Tkus by the substitution of one reptile for another — of the 

 gecko for the crocodile — the well-remembered zoological 

 statement in Arnold's Greek prose is at length put upon a satis- 

 factory foundation. In the spring of 1886, I captured a small 

 gecko [Tarautola mauritauica) at Rome, and I have hitherto 

 succeeded in keeping it alive and in health. One of the first 

 things I noticed about it was the extraordinary vigour with which 

 so small an animal would bite one's finger. And the effect pro- 

 duced was certainly rather due to the lizard's expression of 

 intense ferocity during the process than to the pinch which it was 



',. 2. — The Tarantola prepared 

 to bite, with the upper jaw 

 raised. 



-,. 3.— The Tarantola biting,— a 

 common position, in which the 

 upper jaw is depressed below 

 the normal. 



able to give. The expression chiefly depends upon two things — 

 the fact that the anterior part of the head may be bent down- 

 wards, and that the eyes are retracted into the head. Examin- 

 ing the former movement more carefully, it was seen that in 

 opening the mouth the upper jaw is distinctly although slightly 

 raised above the normal, so that the profile of the upper surface 

 of the head becomes almost straight (comp.ire Figs. I and 2). 

 In biting fiercely it is common for the upper jaw to be depressed 

 below the normal, as is plainly seen in a profile view (compare 

 Fig. 3), although in other positions the curvature of the head i s 



