GERM CELLS IN ASCARIS INCURVA 63 



Flemming-urea mixture;^ Gilson-Carnoy's fluid, Bouin's fluid 

 and for cleavage stages particularly, the alcohol-acetic mixtures. 

 It has been found necessary to adopt a modification of the 

 somewhat laborious methods recommended by de Saedeleer 

 ('12), who divided the thread-like gonads into small pieces 

 from each of which preparations were made. In this work 

 on Ascaris incurva the pieces have averaged 5 mm. in length 

 and in critical areas complete serial sections were obtained. 

 For a study of the spermatogenesis such series have been made 

 from specimens fixed in Hermann's fluid, the Flemming-urea 

 mixture and partial series of limited areas for comparison of 

 critical stages in Gilson-Carnoy's fluid, strong Flemming's 

 fluid and in the alcohol acetic mixtures. For oogenesis a 

 series has been obtained from material fixed in Bouin's fluid 

 and (nearly complete) in the Flemming-urea mixture and for 

 comparisons in Gilson-Carnoy's fluid, strong Flemming's fluid, 

 Hermann's fluid, alcohol-acetic and picro-acetic mixtures. 



Heidenhain's haematoxylin, and the saffranin and light green 

 combinations have been most generally employed as stains 

 but many others for special purposes as mentioned in the text 

 have been used. Schneider's aceto-carmine has proved valuable 

 for making temporary and Mayer's alcoholic hydrochloric- 

 acid carmine for permanent preparations of the cleavage stages. 



OBSERVATIOXS OX CHROMOSOMES 

 A. Spermatogenesis 



1. The spermatogonia. The chromosomes in the sperma- 

 togonial divisions as mentioned in my preliminary note (Good- 

 rich '14) are closely massed (fig. 3) and metaphase plates re- 

 quire considerable extraction in order to distinguish the individual 

 chromosomes. Figure 2 from such a preparation gives a count 

 of 35 chromosomes including the microsome. Figure 1, a, b 

 are from successive sections* of a prophase nucleus showing 34 

 or 35 chromosomes. 



^ I am indebted to Dr. G. L. Kite and to Dr. C. E. McClung for information 

 in regard to tliis fi.xative. 



