74 H. B. GOODRICH 



the X-elements. There have been found in the nucleus no other 

 bodies that could be interpreted as chromatin nucleoli. 



While there can be no doubt as to the presence of chromatin 

 nucleoli and their identity with the X and Y chromosomes in 

 certain insects, this history is by no means so clearly proven 

 for other groups. Most workers on mammalian germ cells 

 have merely mentioned that the nucleolus-like body might be 

 the X-element. For example Wodsedalek ('13 and '14) on the 

 pig and horse, Guyer ('10) and Winiwarter ('12) on man, Stevens 

 ('11) on the Guinea pig and Jordan ('11) on the opposum. The 

 conditions as described in the Guinea-pig and in the opposum 

 are more nearly demonstrative but in no case is the proof so 

 rigorous as in the insects. Among nematodes, Gulick ('11) 

 on Heterakis and Strongilus identifies a nucleolus only in the 

 later growth stages as surely being the X-chromosome ; Schleip 

 ('11) on Angiostomum identifies the X-elements in post-synap- 

 tic nuclei. Mulsow ('12) figures nucleoli of early growth stages 

 of Anc3rracanthus but their history is not traced to the prophases 

 where the X-chromatin seems undoubtedly to exist as a more 

 compact deeply staining body. In Ascaris incurva it may be 

 concluded that the X-chromatin throughout all growth stages 

 exists in a condition indistinguishable from the autosomes. 



C. The seriation 



It has been emphasized in the record of observations that the 

 growth period of both oogenesis and spermatogenesis of Ascaris 

 incurva may be subdivided into the series of stages that has be- 

 come so clearly recognized in other classes of animals. To men- 

 tion a few examples: mammalia, Winiwarter ('00); amphibia, 

 Janssens ('05) ; fishes, Schreiner ('05) ; insects, Davis ('08) ; 

 mollusks, Popoff ('07) ; annelids, Schreiner ('06) ; Sagitta, 

 Bordas ('12), etc., and for which the nomenclature suggested 

 by Winiwarter ('00) so generally accepted, has been used in 

 this paper. Thus to summarize: 



After the post-gonial resting period the nucleus becomes filled 

 with fine threads — the leptotene stage, followed by a stage of 



