35^ 



The Journal of Heredity 



A somewhat different type of lack 

 of precision is shown in numerous in- 

 stances and may be illustrated by this 

 sentence from p. 344, "The 12 pairs 

 of chromosomes in man may in the 

 same wa\- form several million such 

 combinations." Some 18 pages fur- 

 ther on, one learns that there is con- 

 siderable disagreement as to the 

 number of chroiuosomes in man. This 

 lack of care in making unqualified 

 statements is one of the most discon- 

 certing features of the book. 



2. Lack of Accurac\-: On page 362, 

 Fig. 141 we find certain figures copied 

 from Wieman marked as follows: — 

 "A, primary' spermatocyte, negro; B, 

 same, white." The first is a growth 

 period nucleus, the second a first 

 spermatocyte metaphase, consequently 

 the \'er>' striking difference in their 

 appearance can scarcely be attributed 

 to the fact that one is from a negro 

 and the other from a "white." In 

 Wieman 's plates, they are correctly 

 designated. 



Another example which the re\iewer 

 hesitates to mention is in regard to 

 the recognition of the se.\ chromosome; 

 credit is rightly gi\en to Henking 

 (1891) for the discovery that a body 

 which he thought to be a nucleolus or 

 "chromatin bod> " was distributetl to 

 ^2 of the spermatozoa; then follows this 

 statement (p. 358), "It was subse- 

 cjuently shown by Paulmier (1899), 

 Montgf)mer>' (1901), and de Sinety 

 (1901 ) that this l)od>- is not a nucleolus 

 Init an extra or accessor\- chromosome," 

 and tinalK-, "It was at once suggested 

 l)\- McClung (1902), that the accessory 

 chromosome in some way determines 

 sex." As a matter of fact, the term 

 accessory chromosome was introduced 

 by McClung in 1899 and the sugges- 

 tion as to the jirobable function of the 

 chrr>mosome was made b\- the same 

 author in 1901. 



Inacctirracics of tin- kinds referred to 

 so far will df)ub(lcss be largeK' remo\f(l 

 from later editions. A more sericnis 

 feature remains to be considered. 



3. The interpretation of chromosomal 

 beha\'ior at critical stages. On lines 

 f)f work in wlu'cli llic author has not 



engaged the presentation of the facts 

 and the arguments pro and con are 

 usually well given, while conclusions 

 based on his own obser\'ations are 

 certainly not applicable to a great deal 

 of^material which might be used in a 

 c\'tological course. To be specific, his 

 description of the longitudinal splitting 

 of the chromosomes by the formation 

 of a series of vacuoles in the prophase, 

 while coinciding with a great deal of 

 botanical literature on the subject, is 

 in conflict with what clearly takes 

 place in many animals where each 

 chromomere divides. Sharp (p. 155) 

 discredits the existence of chromomeres 

 on the basis of his own work and con- 

 siders the chromatic thread as homo- 

 geneous. The generally accepted view 

 on this subject may perhaps best be 

 indicated by a quotation from Agar's 

 recent cytology. He says in regard to 

 chromomeres (p. 134), "This condition, 

 which forms one of the most character- 

 istic sights met with by the cytologist, 

 can be illustrated by reference to almost 

 any work dealing with mitosis, whether 

 in the soma, germ track of during meio- 

 sis. ... It is equally characteristic 

 of animals and plants." Since genetical 

 e\idcnce leads us to expect just such a 

 linearly arranged series of units as the 

 chromomeres in fact furnish, they are 

 of considerable importance both from 

 the standpoint of heredity and c\-tol- 

 ogy. 



Anotlier position taken by .Sharp 

 which is not satisfactory to one familiar 

 with animal cytolog\- is in regard to the 

 maturation phenomena — again a stage 

 of prime inijiortance from the stand- 

 point of heredity. In common with the 

 majority of botanists. Sharp describes 

 the chromo.somes of the first matura- 

 tion di\ision as bi\-alent in structure. 

 The outstanding characteristic of the 

 prophase of the first maturation di\i- 

 sion is the tetrad or chromo.some com- 

 posed of four e(|ual parts due to the 

 iongitudiiial s|)litting of the synapsed 

 liomologues. .Sharp states (p. 234), 

 "The diakinesis stage is terminated by 

 the dissolution of the nuclear mem- 

 brane and the formation of the spindle, 

 upon which tlu- bi\alenl chromost)mes. 



