THE MATURATION DIVISIONS IN ASCARIS INCURVA. 



H. B. GOODRICH. 



In the following preliminary account of the spermatogenesis 

 and orogenesis of a nematode, Ascaris incurva Rud., it is intended 

 to call particular attention to a remarkable XY-group that 

 forms the extreme case thus far observed. The X-group consists 

 of no less than eight components of which one is a vestigial 

 microsome, while the Y is represented by but a single chromo- 

 some. The nearest approach to this case is that described by 

 Edwards, '10, for Ascaris lumbricoides, where in the heteropolar 

 mitosis the X-element is found to consist of five components 

 unmated by a Y. The extreme example hitherto described in 

 which a Y exists is that of Acholla multispinosa described by 

 Payne, '10, in which case five X-components are opposed by 

 one Y, but here the Y is equal to or larger in mass than the 

 combined X-elements. 



Ascaris incurva is a parasite found in the stomach of the sword- 

 fish, Xiphias gladins L. The material was collected at Woods 

 Hole during the summer of 1913, and most of this thus far studied 

 was fixed in strong Flemming's or Gilson-Carnoy's fluid. 



A study of the spermatogonial cells has proved unsatisfactory 

 as the chromosomes are closely massed and the cytoplasm stains 

 deeply. Counts vary from 33 to 35. Fig. i, showing a cell 

 somewhat over-extracted as is desirable to give the necessary 

 contrast, gives a count of 35 chromosomes including the micro- 

 some. 



During the growth stages a part of the chromatin is massed 

 in a large irregular karyosome. Late prophase or metaphase 

 figures of the first spermatocyte division show 21 chromosomes 

 or 22 if the Y is widely separated from its mate in the X-group 

 (Fig. 2). 



Early anaphase figures of the first spermatocyte division show 

 most clearly the unequal nature of the separation of -the chromo- 

 some groups. Thirteen autosomes lying at or near the periphery 



14? 



