206 



KNOWLEDGE. 



[November 2, 1891. 



satisfactory, interpretation of their appearance. Many 

 fungi of the Mushroom tribe show a tendency to spread in 

 all directions from the spot where tlieir myceHum has first 

 obtained its hold on the soil. They exhaust the soil, so 

 that the grass does not grow well there, but as they 

 spread further out, the place on which they formerly 

 stood produces a luxuriant crop of grass, on account of 

 the extra supply of nutritious matter formed by the decay 

 of their bodies. Thus poor and then good grass follow 

 one another on the same zone of soil. 



Aijaricus campextris is of use to men, but a few of its 

 allies are the dread of the forester, and others are deadly 

 poisonous. It may be remarked in passing, however, that 

 the majority of the cap-fungi are not poisonous, and that 

 more use should be made of the large number of edible 

 fungi which we have in this country. Of these the 

 Mushroom is the only one under cultivation. Mushroom 

 beds are well known to gardeners, and it is not an un- 

 common thing now-a-days to find a range of darkened 

 houses specially devoted to their culture. A curious use 

 has been made of an old railway tunnel — the Scotland 

 Street Tunnel — in Edinburgh. The visitor to this exca- 

 vation will find that, in place of railway sleepers and lines, 

 the ground is occujiied by carefully prepared beds, on 

 which arise luxuriant crops of the favourite Agaric. 

 Although m great request in this country, Berkeley, 

 writing upwards of thirty years ago, states that it is 

 " most carefully excluded from the Italian markets," 

 owing probably to occasional poisoning symptoms that 

 have shown themselves after its consumption. So far as 

 we know, the Mushroom has never been known to have 

 exhibited poisonous properties ia this country. If the 

 Italians are correct, we have a good example of the 

 influence on a plant of its surroundings. 



CROCODILES AND ALLIGATORS. 



By Pi. Lvnf^KKER, B. A. (Cantab. i 



IN spite of the circumstance that numerous examples 

 of those ungainly reptiles known as Crocodiles and 

 Alligators are exhibited in the reptile house of the 

 Zoological Society's Gardens in a living condition, 

 while their stufl:ed skins and articulated skeletons 

 are displayed in the galleries of the Natural History 

 Museum at South Kensington, there appears to be a hope- 

 less confusion in the public mind between these two very 

 difl'erent creatures. And, with the usual perversity of 

 those not acquainted with the ordinary facts of natural 

 history, residents in India increase this confusion by almost 

 invariably speaking of the Crocodiles of that country as 

 Alligators, whereas an Alligator is not to be found from 

 one end of India to another. A remarkable instance of this 

 confusion occurs in Sir S. Baker's " ^Ylld Beasts and their 

 Ways," where, under the heading of Crocodile, it is stated 

 that, " as lizards are found distributed in great varieties 

 throughout the world, in like manner we find the largest of 

 all Uzards, the Crocodile, under various names in nearly 

 every river of the tropics. In America this reptile is 

 generally known as an Alligator, and some persons pre- 

 tend to define the peculiarity which distinguishes that 

 variety from the Crocodile, but I regard the distinction 

 in the same hght as that between the leopard and the 

 panther, the difference existing merely in a name." 



Now, in the first place, although it may be justifiable in 

 popular language to use the term lizard as applicable to all 

 four-footed reptiles except tortoises and turtles, yet, scien- 

 tifically speaking, a Crocodile has not the slightest right 



to be so termed. Indeed, it would be far preferable to 

 speak of a snake as a kind of lizard, since it is really only 

 a special modification of the lizard stock ; and from a 

 strictly scientific point of view it would imply far less con- 

 fusion of ideas to call a coNv a kind of pig than to term a 

 Crocodile a lizard, since whereas a cow and a pig are 

 mammals belonging to the same section of a single order, 

 lizards and Crocodiles represent two totally distinct oitlete 

 of reptiles. With regard to the statement that the dif^ 

 fereuce between a Crocodile and an Alligator is merely one 

 of name, the reader who follows us through this article 

 will probably hold a difl'erent opinion by the time he reaches 

 the end. 



So far as external appearance goes, most people are 

 aware that Crocodiles and Alligators are large, long-tailed, 

 low-bodied reptiles, with flat and frequently broad heads, 

 and their bodies protected by a coat of scales, which vary 

 greatly in size in its difl'erent regions. They probably also 

 know that it is the impressions of these scales, or of the 

 bony scutes by which those of the back are underlain, that 

 form the well-known markings on the Crocodile-skin now 

 so commonly used for bags and other leather articles. In 

 their short and clawed limbs there are five toes in the 

 front pair, and four in the hinder, those of the latter being 

 connected together for a part of their length by a web. As 

 regards their habits. Crocodiles and Alligators are typical 

 amphibioits creatures, being perfectly at home in the water, 

 but also capable of active progress on land, on which their 

 eggs are laid and the young hatched. The position of 

 then- external nostrils at the very tip of the snout enables 

 them to come to the surface for the purpose of breathing 

 without showing more than their muzzle, or, at most, this 

 and their somewhat prominent eyes. These external 

 characters will enable us to recognize an Alligator or 

 Crocodile when w-e see it, and yet do not show us how 

 these creatures difl'er so essentially from true lizards as to 

 render it incorrect to speak of them merely as a parti- 

 cular group ot lizards. To render this essential distinction 

 apparent we must enter into certain details of their ana- 

 tomical structure, more especially as regards the skull. 

 Now, in the first place, a Crocodile or Alligator may be 

 at once distinguished from every true lizard by the 

 circumstance that its large and pointed teeth are inserted 

 in the jaws in distinct and separate sockets, from which 

 they will readily fall out in a dried skull : whereas 

 those of lizards, which vary gi'eatly in form, are in- 

 variably united by solid bone with the edges or 

 sides of the jaws, without any separate sockets. More- 

 over, in a Crocodile's shell, there is a bar of bone running 

 backwards from the lower border of the eye-socket, or 

 orbit (Fig. 1, <>), to join the condyle with which the 

 lower jaw articulates. This bar is seen in Fig. 1, below, 



Fig. 1. — Side view of tKe skull of a Crocodile ; 

 O, eye-socket or orbit. 



and to the left of the letter O, and also occupying the 

 same relative position in Fig. 8. It will further be 

 apparent fi-om the latter figure that in a Crocodile's skull 

 there are two parallel bars running backwards from behind 

 the orbit, of which the upper one is the stoutest. Now 

 in a Uzard's skuU, only the uppermost of these two bars 

 is present ; and we thus have a second important distinc- 



