REVIEWS 167 



The account given of the general nature of the germ-cells is too compressed 

 to be properly intelligible to a beginner, and it is difficult to see what object 

 is gained by its inclusion. The words " ovogenesis," " ovogonia," and " ovocyte" 

 are objectionable. 



The developmental processes prior to laying and during the first three days 

 of incubation are treated by stages, and form the subject-matter of Part I. The 

 later developmental history, on the other hand, is dealt with according to the 

 organs concerned, and is included in Part II. The second chapter, dealing with 

 the development before laying, is particularly interesting, since it embodies 

 accounts of the original researches of Dr. Mary Blount and J. T. Patterson, 

 which were undertaken especially for this work. Miss Blount has worked out 

 in detail the cleavage processes in the egg of the pigeon, and has found that 

 there is an accessory cleavage in the marginal zone or periblast, which surrounds 

 the segmental area. The nuclei in the periblast are shown to arise from super- 

 numerary sperm nuclei, which accumulate and multiply in this zone, but afterwards 

 degenerate. This and other facts have been brought to light by Miss Blount's 

 investigation. The process of gastrulation and the formation of the primitive 

 streak in the pigeon have been fully worked out by Patterson, who inter- 

 prets the first stage in the formation of the entoderm as an ingrowth of the 

 free margin of the blastoderm, as supposed by Haeckel and others. In support 

 of this view, Patterson states that the antero-posterior diameter of the blastoderm 

 is shorter than the transverse diameter during the process in question, whereas 

 previously the blastoderm was approximately circular. Moreover, experiments 

 showed that injuries to the margin made just prior to gastrulation appear later 

 in an anterior position in the entoderm. Patterson says also that the thickening 

 of the margin is brought about not so much by a multiplication of cells in situ as 

 by an immigration of cells from the sides. These facts are of interest, but it 

 is doubtful whether the beginner will be able to appreciate their significance. 



The results of other recent investigations are mentioned in their proper places. 

 Thus, Eycleshymer's observations on the temperatures of the hen and egg during 

 incubation, and Locy's researches on the fifth and sixth aortic arches, are duly 

 referred to, and there is a fairly complete bibliography at the end of the volume. 

 The work has been written directly from the material in nearly every part, 

 and the result is that, for an elementary text-book, it is of an original character 

 throughout. It is admirably illustrated, and the majority of the figures are 

 new, having been drawn or photographed from original preparations. Attention 

 may be called also to the chronological tables of development, which should prove 

 very useful to the student. In conclusion, we have no hesitation in congratulating 

 both author and publishers. 



Francis H. A. Marshall. 



Recent Advances in Organic Chemistry. By A. W. Stewart, D.Sc. With 

 an Introduction by J. Norman Collie, Ph.D., LL.D., F.R.S. [Pp. xv + 296.] 

 (London : Longmans, Green & Co. Price ys. 6d. net.) 



" Speaking exclusively of observational and experimental sciences, it is obvious 

 that progress can be accomplished only at the cost of destroying or modifying 

 current theories." 



" Without any disrespect, it may be stated that the majority of scientific investi- 

 gators are not possessed of strikingly original minds." 



"The last twenty years of organic chemistry, however, have been rather barren 

 in many directions. The reason for this is most probably to be sought in the 



