August 30, 1912] 



SCIENCE 



285 



ing according to most of our notions regard- 

 ing a pathogenic organism, has likewise not 

 up to the present been proven to be the cause 

 of leprosy, although I am impressed with the 

 probability of such a role being eventually 

 attributed to it, and consider that it deserves 

 more serious attention than any strain so far 

 cultivated from the human leprous lesion. 



The wide variation in morphology and 

 staining reaction for the culture recovered 

 from the human leprous lesion which subse- 

 quently becomes a rapid grower and chromo- 

 genic, might account for the interpretations 

 of Kedrowski, Eost, Williams, Bayon and 

 others that B. lepras is a bacterium of such 

 pleomorphism that it can be recognized as a 

 non-acid-fast diphtheroid, or streptothrix, and 

 as an acid-fast bacillus. 



Charles W. Duval 



the lagomoephs an independent order 

 The order Eodentia, as at present under- 

 stood, includes two great groups, or suborders, 

 commonly called the Duplicidentata and the 

 Simplicidentata. Marked distinctions be- 

 tween these groups have long been recognized, 

 yet they have been retained in a single order 

 because of (1) a similar development of large 

 scalpriform incisors and (2) certain similari- 

 ties in the morphology of the brain and repro- 

 ductive system which have been regarded as 

 determining relationship. It has been argued^ 

 that these similarities the more surely denote 

 relationship because of their deep-seated na- 

 ture. When it is remembered, however, that 

 in development of both brain and reproductive 

 system the groups under discussion are very 

 primitive, differing in these respects but 

 slightly from the Inseetivora, Chiroptera, 

 Edentata and Marsupialia, these similarities 

 lose much of their significance, and seem to 

 be far outweighed by the many differences of 

 other early acquired anatomical specializa- 

 tions, especially of the skull and feet. These 

 differences gain in importance when it is con- 

 sidered that, whereas the Simplicidentata are 

 an exceedingly diversified group, both in life 

 ^ Gregory, Bull. Amer. Mus. Nat. Hist., Vol. 27, 

 p. 325, 1910. 



and food habits and consequent morphological 

 modifications, while both groups have an 

 almost world-wide distribution, yet there are 

 no known connecting links or intermediate 

 forms, either living or extinct, even though 

 such forms as the jerboas among the true 

 rodents have outstripped the Lagomorphs in 

 specialization for the leaping mode of progres- 

 sion. Paleontological evidence is admissibly 

 very incomplete, yet so far as it goes it indi- 

 cates clearly two important facts : first that 

 both groups under discussion are of very an- 

 cient origin, the known forms showing but 

 slight modification from the early Oligocene 

 up to the present day, and second that in both 

 groups the scalpriform incisor teeth were very 

 early acquired. The latter fact through early 

 limiting their food habits to a certain degree 

 may account in a large measure for the reten- 

 tion in each group of similar primitive char- 

 acters. In other and widely differing orders 

 scalpriform incisors have been independently 

 acquired, as in the toxodonts, the pyrotheres, 

 the lemurs {Daubentonia, aye-aye), the al- 

 lotheres (Polymastodon), the tillodonts and 

 the hyracoids. Even among the artiodac- 

 tyls a close approximation to this form of 

 incisor has been reached, in the lower jaws, 

 by such forms as the Uama and the aberrant 

 goat, Myoiragus. This character, therefore, 

 is not peculiar to the lagomorphs and rodents, 

 and may very well have been quite indepen- 

 dently acquired by these groups. Moreover, 

 certain peculiarities in the structure and de- 

 velopment of the incisors in the lagomorphs 

 suggest the truth of this assumption. 



Since, therefore in our present state of 

 knowledge there is apparently no good reason 

 for continuing the association of these two 

 great groups of mammals and since, owing to 

 the great number of important differences 

 between them, it is far more convenient for 

 purposes of classification and comparison with 

 other forms to consider them separately, there 

 seems ample reason for placing the Duplici- 

 dentata in an independent order. This new 

 order may be called the Lagomorpha, adopting 

 the old subordinal name given to this group 

 by Brandt. 



