THE OVUM OF THE NINE-BANDED ARMADILLO. IO3 



with some assurance to enumerate the elements of the chromo- 

 some complex. This should furnish a useful companion study to 

 that of the spermatogenesis which is being worked out by Dr. 

 J. T. Patterson. Finally, the facts here presented serve to 

 banish any hesitation that may at any time have been entertained 

 as to the validity of the assumptions upon which are based the 

 studies of the predeterminative and epigenetic factors concerned 

 in the development of the definitive characters of the armadillo 

 quadruplets, studies which were outlined in a former publication 

 (Newman and Patterson, 'n) and which are at present being 

 carried on with a much more adequate collection of material. 



II. LITERATURE ON MAMMALIAN OVOGENESIS. 



Considered solely as a contribution to our knowledge of the 

 maturation and fertilization processes of mammalian ova the 

 present study would be well worth presentation owing to the 

 fact that the work in this field has been confined to three orders 

 of mammals, Rodentia, Cheiroptera and Carnivora. Nothing is 

 know r n of the conditions in any Edentate. It is a pleasure then 

 to add to this brief list not only an additional order but one in 

 which the ovum is of a type more primitive than any previously 

 noted for Eutheria. 



Our knowledge of ovogenesis in the Cheiroptera is limited to one 

 species, Vesperugo noctula, described by O. Van der Stricht in 

 1909. The only representative of the Carnivora which has 

 received adequate attention is the domestic cat, the maturation 

 and fertilization of which have been recently worked out in detail 

 by Longley ('11). The rodents however, have furnished the 

 basis for numerous elaborate studies. Conditions in the guinea- 

 pig, the rat and the mouse are known in detail and especially 

 is this the case with the mouse, upon which no less than eight 

 investigations have been published. All of this rather volumi- 

 nous literature has been recently reviewed by several authors 

 and for details the reader is referred to the papers of Kirkham ('07), 

 Sobotta and Burckard ('10), Long and Mark ('11) and Longley 



('II). 



We have then adequate accounts of the ovogenesis of only five 

 species of mammals: the bat, the cat, the guinea-pig, the rat 



