June 8, 1917] 



SCIENCE 



591 



tration of lectures — that most important 

 change of emphasis which came to pass in the 

 method of scientific education. Professor 

 Cross has won high place, which he will hold, 

 whether or not in retirement. — Boston Even- 

 ing Transcript. 



SCIENTIFIC BOOKS 



The Birds of Britain, their Distribution and 

 Habits. By A. H. Evans, M.A., F.Z.S., 

 M.B.O.IJ., Cambridge, 1916. 8vo, pp. xii + 

 275, numerous halftone text-figures. 

 This concise and rather informal work is 

 stated to be " primarily intended for schools," 

 but is designed also to serve as a " short hand- 

 book which includes the results of the most re- ^ 

 cent observations, and is adapted to modern 

 nomenclature." While this intention may be 

 justified by the character of the main text, the 

 introductory chapter, treating of " The Class 

 Aves, or Birds in General," might have been 

 written a generation ago, and does not include 

 "the results of the most recent observations," 

 as regards especially the subject of migration. 

 Reference is made only to the creditable work 

 of local observers in Britain, which has ac- 

 cumulated interesting facts regarding the 

 movements of birds in England and Wales 

 without furnishing generalized results, while 

 the important work carried on elsewhere is 

 passed without mention, including the re- 

 searches of the late W. W. Cooke which have 

 so greatly extended our knowledge of this sub- 

 ject. 



In the main text, under the general heading 

 " Classification," with subheadings for the 

 higher groups from orders to subfamilies, a 

 paragraph, without special heading, is devoted 

 usually to each species of regular occurrence in 

 Britain, with a nominal- list at the end of 

 nearly 200 " occasional visitors " not formally 

 mentioned in the preceding pages. The au- 

 thor manages to give in the half-page notices 

 of the species of regular occurrence a compre- 

 hensive statement of their leading traits, dis- 

 tribution and diagnostic features, in a clear 

 and direct way that should render his " little 

 book" attractive and useful to many readers. 

 The nomenclature is strictly modern, being 



" almost exactly " that of the British Ornithol- 

 ogist's Union's revised Check-list. The illus- 

 trations, though said to be " from photographs 

 taken for the most part from nature," are in 

 many cases obviously not from life but from 

 stuffed specimens or from museum groups, and 

 are thus not up to the standard of the text. 



J. A. A. 



SPECIAL ARTICLES 



FACTORS IN THE GROWTH AND STERILITY OF 

 THE MAMMALIAN OVARY 



1. The growth and, to some extent, the 

 structure of the mammalian ovary depend 

 essentially on the development of the ovarian 

 follicles. The maturation of some follicles and 



\the subsequent rupture leads to the formation 

 of the corpus luteum; the retrogression 

 (atresia) of follicles before they have reached 

 maturity and ruptured leads in certain species 

 to the formation of the so-called interstitial 

 gland and in others to the accumulation of 

 atretic follicles in which the theca interna is 

 relatively prominent, without, however, the 

 formation of an interstitial gland. 



As we shall see presently, it is possible to 

 inhibit the full development of the follicles 

 experimentally. Under these conditions we 

 find 'that the atretic follicles with relatively 

 large thecEe interna, are especially numerous 

 and constitute perhaps the greater part of 

 the ovary. We may therefore conclude that 

 it is the pressure exerted by the developing, 

 expanding follicles which leads to the shrink- 

 ing and ultimate complete disappearance of 

 the atretic follicles, and that if this pressure 

 is diminished these atretic follicles become 

 relatively prominent. This explains their 

 relative preponderance in the guinea pig dur- 

 ing the period following ovulation, when no 

 large follicles are present, in the ovaries. 



2. Former observations of the writer showed 

 that under certain conditions mitoses in the 

 granulosa cells of the follicles were especially 

 frequent around the ovum. This suggested 

 the possibility that the stimulus for the grovrth 

 of the granulosa cells which ultimately deter- 

 mines the growth of the whole follicles, de- 

 pends upon a substance given off by the 

 ovum. Dr. L. S. N. Walsh in our laboratory 



