86 H. B. GOODRICH 



that the two types of spermatids receive respectively fourteen 

 and twenty-one chromosomes. For a more correct estimate 

 of mass the microsome should be omitted, the long X-component 

 given a double value, but this does not change the ratio. Models 

 have been made of the metaphase plates of the second spermato- 

 cyte divisions and these have been weighed and gi^'e an average 

 ratio of 14 : 21 between the two types. Thus there exists a 

 marked relation between the nuclear volumes and the number 

 of chromosomes contributed to the two types of spermatids. 

 The correlation is close considering the difficulties of measure- 

 ment and realizing that individual chromosomes vary in size. 

 The correlation of the observed and expected ratios is no more 

 close than those reported by Zeleny and Faust ('15) or Wodse- 

 dalek ('13 and '14) but the separation of the modal points is 

 here proportionally much greater.'' There therefore is less 

 doubt that the bimodal character of the curve is significant 

 and as the expected ratio is also greater and closely proportional 

 to the observed ratio, the results support the conclusion of these 

 writers that the size dimorphism is a result of the chromosomal 

 dimorphism of the spermatids due to the presence or absence 

 of the sex chromosomes. 



THE EARLY CLEAVAGE 



The cleavage as far as followed proceeds as in Ascaris megalo- 

 cephala (Boveri '99). 



I have been unable to obtain preparations favorable for study 

 of the chromosomes in cleavage. They are closely massed 

 and irregular in form. Chromatin diminution, however, occurs 

 in the somatic cells. Text figures F-K are semi-diagrammatic 

 and based on total preparations, stained in aceto carmine or in 

 alcoholic, hydrochloric acid carmine. These show anaphase 

 spindles of all divisions to the eight cell stage. These show 

 that the diminution occurs as in Ascaris lumbricoides during 

 the third cleavage (Meyer '95, Bonevie '02) rather than as in 



^Zeleny and Faust ('15) the highest ratio of 35 forms is 1.00 : 1.12; Wodse- 

 dalek ('13) on the pig 1.00 : 1.20; ('15) on the horse 1.00 : 1.05. In Ascaris incurva 

 ratio equals 1.00 : 1.40. 



