GERM CELLS IN ASCARIS INCURVA 77 



cates the more accepted theory but in both of these cases the 

 conclusion is based on studies of the prophases or immediately 

 preceding stages and it seems clear that a theory of maturation 

 cannot be convincing unless it includes an interpretation of 

 the processes that take place during the whole growth period. 

 Tretjakoff also supports a theory of normal reduction but, as 

 Gregoire has mentioned, his figures are difficult to interpret 

 and he has made no detailed study of the earliest stages — the 

 leptotene and contraction nuclei, incorrectly, I believe, identify- 

 ing another stage with this latter phase. "^ 



The establishment of the accepted seriation of stages for the 

 genus Ascaris is of significance, for in those forms which exhibit 

 this seriation and which are more favorable for study, the evi- 

 dence indicates that these stages prepare for a true reduction 

 division, and therefore the presumption is strong, that in other 

 forms less favorable for a detailed analysis but which show 

 a like seriation, the processes are the same. 



D. The pro-chromosomes and synapsis 



The chromatin bodies of the pro-synaptic nucleus (fig. 5) 

 show a marked resemblance to the pro-chromosomes described 

 by Overton ('05, '09) in Podophyllum. The condition of ex- 

 treme condensation of the chromatin masses is not often ob- 

 served in Ascaris incurva, more frequently cells are found in 

 the .condition shown in figure 6 which may be compared with 

 a similar stage in Acer, Salmonica, Botrychium (Cardiff '06) . 

 or in Calycanthus (Overton '09), showing the chromatin some- 

 what distributed upon the parallel threads. This indicates 

 either that the pro-chromosome stage of Ascaris incurva is of 

 short duration or that there merely exists at this period a tendency 

 towards the extreme condensation which may not always be 

 realized. The process of change from this condition to the lepto- 

 tene stage may be analogous to the um-aveling of the massive 

 bodies described by Janssens ('01), Davis ('08), Wilson ('12) 

 and others, to form the leptotene threads. In A. incurva, how- 



^ A more detailed review of these studies is given by Geinitz '15. 



