486 



SCIENCE 



[N. S. Vol. XL VI. No. 1194 



time, it should not be forgotten that most of 

 the physicians now in the Medical Eeserve 

 Corps have not only left the comforts of their 

 homes, but also have given up practises which 

 in the majority of instances yielded far more 

 income than the pay they would receive as 

 medical officers of the Army even if they had 

 conferred on them the highest rank that the 

 proposed law would provide. Among these 

 medical reserve officers are many of the most 

 prominent men in our profession, including 

 the leading men in the specialties, as well as 

 our best surgeons and internists. 



When the war broke out there were less than 

 450 medical officers in the regular Army Medi- 

 cal Corps. To-day there are commissioned, 

 including officers of the regular Army, the 

 National Guard and the Medical Eeserve 

 Corps, at least 1Y,000 physicians. Less than 

 1,000 are in the regular Army Medical Corps. 

 Under the present law these regular Medical 

 Corps officers are entitled to the grades of 

 lieutenant-colonel and colonel; and in the case 

 of the surgeon-general, to that of brigadier- 

 general ;i the highest rank that can be con- 

 ferred on any one of the other 16,000 — that is, 

 on any reserve medical officer — is that of 

 major. 



May we remind our readers that the men in 

 active service will be prevented by the regula- 

 tions from using their influence in this 

 matter, and that the duty of pushing this 

 measure rests on those who stay at home? 

 Every physician has representing him in Con- 

 gress one man in the House of Representatives 

 and another in the Senate. If every phys- 

 ician will let his representatives know that 

 this proposed measure should become a law, 

 and if in addition he will enlighten his 

 neighbors in regard to the matter, an effective 

 public opinion will be created. The time is 

 opportune; congressmen are at their homes. 

 Write or speak to your representatives now; 

 get your neighbors to do likewise — not for the 

 good of the medical profession, but for the 

 good of the service. — The Journal of the 

 American Medical Association. 



1 Surgeon-General Gorgas has the rank of major- 

 general by special act of Congress. 



SCIENTIFIC BOOKS 



The Biology of Twins. By Horatio Hackett 

 Newman, Associate Professor of Zoology, 

 and Dean in the Colleges of Science, Uni- 

 versity of Chicago. University of Chicago 

 Press, 1917. Pp. 1-185. 55 figures in the 

 text. 



Polyembryony, or the production of more 

 than one individual from a single fertilized 

 egg, although a phenomenon occurring con- 

 stantly in some groups of animals, and occa- 

 sionally in others, including man, is as yet un- 

 mentioned in our test-books of general zool- 

 ogy, where the impression is given, or the 

 statement even definitely made, that, except as 

 the result of experiment, a single zygote, re- 

 sulting from a normal fertilization, invariably 

 results in the formation of a single individual. 

 That in the Texan armadillo a single egg 

 always produces four individuals, and that a 

 much more numerous progeny results from a 

 single egg in certain of the gall-wasps (Copi- 

 dosoma), are facts that are now forcibly 

 brought to the attention of zoologists through 

 the long and arduous labors of the two asso- 

 ciates, H. H. Newman and J. W. Patterson. 



While the original papers are necessary for 

 one seeking the details, the essential points ob- 

 tained by these and other investigators to date 

 have been placed in a single small volume 

 where, appearing in a not too technical dress, 

 they are readily and conveniently available, 

 not to zoologists alone, but to the thinking 

 public in general. 



The work is based upon the Texan armadillo 

 (Dasypus novemcinctwni), which produces 

 four young at a birth, all of the same sex. 

 After an introduction and a preliminary chap- 

 ter, setting forth what is commonly known 

 concerning twins in general, mainly human, 

 and their probable relation to double monsters, 

 there follows in Chapter II. an almost complete 

 sketch of the development of the nine-banded 

 armadillo. This sketch includes " the whole 

 range of stages from ovogenesis to birth, with 

 but one gap which, it is hoped, the near future 

 will see filled in." This gap is that of the 

 early cleavage stages, but as a partial substi- 

 tute for these Newman refers to his paper of 



