May 5, 1899.] 



SCIENCE. 



631 



ume is a simple schematic representation, 

 I venture even to say a little too schematic- 

 Each object is designated by a number, and 

 the corresponding name is to be sought in 

 the special tables of regions, canals and 

 oases. This makes the use of the chart 

 troublesome and comparison with other 

 charts inconvenient. All the lai'ge and 

 small canals, of whatever degree of impor- 

 tance and visibility, are treated in a uniform 

 manner and are represented by lines of 

 equal intensity ; and tlie same with the 

 oases, with the exception of the largest one 

 of all, called the Lake of the Sun. It is 

 not easy to recognize promptlj^ on the chart 

 many of the objects which are ordinarily 

 seen at the first glance and which are fa- 

 miliar to areographers. Such objects as 

 Indus, Oxus, Ganges, Cyclops, Trivium and 

 Elisium must be sought in an inextricable 

 maze of lines. We have here not a simple 

 index, but one which in use requires itself 

 an index. 



I will close this incomplete description 

 of the work on Mars at Flagstaff with the 

 expression of a hope and a wish, namely, 

 that so important a publication should not 

 be limited to a single opposition. The 

 exact and complete knowledge of Martian 

 phenomena demands that the planet should 

 be examined under all possible inclinations 

 of its axis and during all seasons of its 

 year. This requires observations continued 

 at least through seven consecutive opposi- 

 tions. I say, ' at least,' for if the terrestrial 

 seasons are far from following the annual 

 period with mathematical precision, the 

 phenomena of Mars seem still more diver- 

 gent ; and the existence of other periods, 

 longer and more complex, ought to be in- 

 cluded among the possibilities. Neverthe- 

 less, I think that if we could have before 

 us seven volumes similar to the one under 

 review, and corresponding to a complete 

 cycle of seven oppositions, many facts 

 would be revealed of which we are at pres- 



ent ignorant, and many others of which we 

 have at present only dubious indications ; 

 especially would this be the case if the 

 seven volumes were the work of the same 

 observers. I therefore hope and wish, as 

 do many others, that Mr. Percival Lowell 

 may be in a position to continue the work 

 so happily begun ; that he will soon publish 

 the results of the observations during the 

 opposition of 1896-97, and that the same 

 means which he has employed for the study 

 of the southern hemisphere of Mars may be 

 applied to the still more important obser- 

 vation of the phenomena of the northern 

 hemisphere.* 



G. SCHIAPAEELLI. 



Milan, March 1, 1899. 



ON THE DEVELOPMENT BY SELECTION OF 

 SUPERNUMERARY MAMMAE IN SHEEP.t 



In the year 1890 Dr. Bell found that 50 % 

 of the lambs born upon his farm in Nova 

 Scotia were twins, and he made an exam- 

 ination of the mothers in order to ascertain 

 whether the twin-bearing ewes differed in 

 any noticeable degree from those which 

 produced single lambs. 



Thirty-three percent, of the twin-bearing 

 ewes were found to possess supernumerary 

 mammae in a more or less rudimentary con- 

 dition, whereas among the ewes having 

 single lambs only 22% possesssed the pecul- 

 iarity ; 43 % of the ewes having supernu- 

 merary mammas bore twin lambs, whereas 

 only 30% of the normally-nippled ewes 

 had twins. 



Although the absolute numbers were far 

 too small to yield reliable percentages, they 

 afforded some ground for the idea that the 

 extra-nippled ewes were more fertile than 

 the others ; and Dr. Bell thought it would 

 be interesting to ascertain (1) whether by 



* Translated from the author's MS. in French by 

 E. B. F. ' 



t Abstract of a paper read before the National 

 Academy of Sciences at Washington, D. C, April 

 19, 1899, by Alexander Graham Bell. 



