Marcu 25, 1915 | 
NATURE 
89 

As in the case of his volume on the ‘Laws of 
Wages,” Prof. Moore brings a distinct freshness 
of view to his task, and has made an important 
contribution to the subject with which he deals. 
What one most misses is any reference to the 
labours of others who have preceded him in the 
same field, and rendered the hypothesis one that 
many have already accepted, though some of 
them may only be willing to regard the weather- 
cycle as a contributory cause. 
Directions for a Practical Course in Chemical 
Physiology. By Dr. W. Cramer. Second 
edition. Pp. viii+1o2z. (London: Long- 
mans, Green and Co., 1915.) Price 3s. net. 
Tuts is a useful little laboratory manual, in 
which the author states he has departed from 
the method usually employed. This departure 
may be illustrated by an example; there are cer- 
tain tests for starch; it is usual to take com- 
mercial starch and perform the tests with this; 
the student is generally instructed also to prepare 
enough starch from the potato to illustrate its 
microscopic appearances. Dr. Cramer adopts the 
method of starting with the potato, and instructs 
his pupils to prepare from _ it 
enough starch for macroscopic ex- 
periments also. The distinction be- 
tween the two methods is rather 
apparent than real, and Dr. 
Cramer’s method involves more 
trouble to the student, which may 
not be a bad thing. Another de- 
parture one notices is that the 
results of a reaction are not ex- 
plained; he interpolates instead 
questions such as, what change 
occurs? or why is this? or explain 
the result. This plan of stimulat- 
ing inquiry is an excellent one for the student 
above the average; but one fears that 95 per cent. 
of the class will leave the questions unanswered, 
and be content with their ignorance. The author, 
moreover. is not consistent in the use of this 
method of questioning; one notes, for instance, in 
such subjects as blood-clotting and nerve chem- 
istry, subjects on which Dr. Cramer holds special 
views of his own, that the teaching is didactic; 
it would evidently be unsafe to leave students 
here free to pursue independent inquiry. 
We DH. 
Soil Conditions and Plant Growth. By Dr. E. J. 
Russell. Pp. viii+190. New edition. Mono- 
graphs on biochemistry. 
Green and Co., 1915.) 
THE first edition of Dr. Russell’s book was re- 
viewed in the issue of Nature for October 24, 
-Ig12 (vol. xc., p. 215). To the new edition a 
chapter has been added on the relationship be- 
tween the micro-organic population of the soil 
and the growth of plants, and also a number of 
sections dealing with recent developments of other 
parts of the subject. 
NO. 2360, VOL. 95] 
(London: Longmans, 
Bricems se 
LETTERS .VO THE EDITOR: 
[The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications. | 
Early Figures of the Opossum. 
In view of the fact that several communications 
have appeared in Nature during the past year con- 
cerning the first mention of the American opossum 
in literature, it may not be inopportune to direct 
attention to some of the early illustrations of this 
animal in maps and in printed works. First of all, it 
should be stated that the earliest reference to the 
opossum is found in the famous collection of voyages 
known as ‘‘ Paesi Novamente Retrovati,’”’ published in 
1507. In chapter cxiii. of that work it is mentioned 
that a live specimen, taken by the Pinzons in Brazil 
in 1500, was exhibited in Granada. 
In the Waldseemiiller map of 1516 a drawing in- 
tended to represent the opossum, as indicated by its 
accompanying legend, is introduced in the Brazilian 
region of South America; and this figure is copied 
in a number of later maps, and also in the Italian 
edition (1558) of Sebastian Miinster’s ‘‘Cosmo- 
graphia.” 


” 
Under the native designation of ‘“‘Su,” a grotesque 
| figure of the opossum was given by André Thevet, 
in his volume published in 1558, and in the same 
year appeared the ‘‘ Wahrhaftig Historia’ of Hans 
Stade, of Homburg, wherein occur (cap. xxxi.) two 
illustrations, and descriptions, of these Brazilian 
animals, one of which is called the ‘Servoy”’ 
(Didelphis marsupialis, L.) and the other ‘ Dattu” 
(Dasypus novemcinctum). The descriptions read as 
follows :— 
“There is also a kind of game, called servoy, 
| which is as large as a cat, and has a tail like a cat; 
its fur is gray, and sometimes grayish black. And 
_ when it breeds, it bears five or six young. It has a 
| slit in the belly about half a span in length. Within 
the slit there is yet another skin; for its belly is not 
open, and within this slit are the teats. Wherever 
it goes, it carries its young in the pocket between the 
two skins. I have often helped to catch them and 
have taken the young ones from out of the slit.”” 
“There is another sort of animal found in this 
country which the savages call dattu; it stands about 
six inches high and is nine inches long; its body is 
| covered all over, except underneath, with a kind of 
| armor. This covering is horn-like, and the plates 
| overlap one another like those of chain armor. This 
animal has a very long snout, and is usually found 
on rocks. It feeds on ants. Its flesh is sweet and I 
| have often eaten of it.” 
