THE CELL MECHANISM 



A Review of Sharp's Cytology 



THE present condition of cytolog>^ 

 as one of the most actively 

 developing biological sciences is 

 indicated by the appearance in little 

 more than a year of three new text- 

 books on the subject, two from England 

 and the American one which is the 

 subject of this review.^ The source 

 of this increasing interest in morphologi- 

 cal cytolog>' evidently lies in its 

 inter-relations with genetics and with 

 cell physiology. 



Professor Sharp's book is well 

 planned and modern in its view-point. 

 It gives an adequate historical back- 

 ground and extensive bibliographies; 

 each of the general subjects treated is 

 followed by a bibliography which 

 should render available a complete list 

 of titles to anyone who followed up 

 those given. It is efficiently indexed, 

 all generic names in the index are fol- 

 lowed by some word showing the 

 general systematic position of the 

 organism. This is a feature which 

 will be found very convenient. The 

 book is well balanced; some 214 pages 

 deal with such subjects as "Proto- 

 plasm," "Metaplasm," "Polarity," 

 "Plastids and Chondriosomes," etc.; 

 86 pages are devoted to the chromo- 

 somes; and the last 104 pages to the 

 theories and laws of heredity and the 

 relation of the latter to the chromo- 

 somal mechanism. 



A number of the text-figures are 

 diagrams which show the behavior of 

 the chromosomes with the greatest 

 simplicity. Indeed, to the reviewer, 

 certain diagrams like those on pages 

 228 and 229 where, for the sake of 

 clearness, the second maturation divi- 

 sion is not represented, seem to have 

 gone too far in this direction. Other 

 diagrams are excellent, e. g., the two 

 on page 341 which give the parallelism 

 between the distribution of an allelo- 

 morphic pair of Mendelian characters 



and of a homologous pair of chromo- 

 somes. 



For the majority of the readers of 

 this Journal, the parts dealing with 

 the chromosomes and heredity are the 

 ones of most interest and, so far as the 

 principles involved are concerned, they 

 are presented in such a way that it 

 would seem that a person with no 

 technical training in either cytology 

 or genetics could read the book and 

 grasp them. However, the real use- 

 fulness of the book depends on its value 

 as a cytology text and a close inspection 

 from this standpoint leaves one disap- 

 pointed in several respects. A first edi- 

 tion of a book of such wide scope almost 

 inevitably contains some errors. This 

 one presents a rather large number, and 

 it seems necessary to consider these at 

 some length because this work comes 

 nearer to meeting a definite need for a 

 text-book of cytology than any other 

 available. 



The chief difficulties will be con- 

 sidered under three headings with brief 

 examples. 



1 . A lack of clearness and precision 

 of expression. Usually an experienced 

 cytologist could arrive at the meaning, 

 but a thoughtful beginning student will 

 meet considerable difficulty with a 

 sentence such as this, pp. 351, "If — 

 the mutation is such as to result in a 

 recessive character, this character does 

 not manifest itself until it meets a 

 similarly mutated gene in the homo- 

 zygous individual." In this brief sen- 

 tence, there is evidently confusion as to 

 character and gene, while the meaning 

 of the latter part of the sentence can 

 only be surmised. Perhaps one of 

 the ideas is that when two gametes 

 each bearing similar genes for some 

 character meet they give rise to an 

 individual homozygous for that char- 

 acter. 



1 Introduction to Cytology, by Lester W. Sharp, Ph.D. pp.452 with 152 text-figures. New 

 York, McGraw-Hill Book Co. 1921. 



351 



