128 H. H. NEWMAN. 



chromosomes appear to afford exceptional opportunities for 

 enumeration. The haploid number appears to be 16 and the 

 diploid, 32. There are numerous apparent exceptions, but 

 these are the most commonly appearing numbers. 



7. The second polar spindle and second polar bodies are of 

 rare occurrence, but those studied are in no way different from 

 those of other mammals. 



8. An exceptional case of what appears to be a third matura- 

 tion division is figured and discussed. 



9. A single tube egg in a good state of preservation shows a 

 late stage in the fertilization process. Both polar bodies are 

 present, and the male and female pronuclei are large vesicles 

 practically ready for fusion. This one case is adjudged to be 

 typical and, on the basis of its discovery, we are in a position to 

 add another item to the evidences already published that the 

 quadruplets of the nine-banded armadillo are derived from a 

 single fertilized egg. The case also serves to eliminate from 

 further consideration all suggested explanations of the underlying 

 basis of polyembryony that involve the idea of polyspermy. 



HULL ZOOLOGICAL LABORATORY, 



UNIVERSITY OF CHICAGO, 

 May i, 1912. 



LITERATURE LIST. 



1. Coe, W. R. 



'08 The maturation of the egg of the rat. Science, N. S., Vol. 27, No. 690. 



2. Hill, J. P. 



'10 The early development of the Marsupialia, with special reference to the 

 native cat (Dasyurus viverrinus). Quart. Journ. of Microsc. Sc., Vol. 56, 

 Part i. 



3. Kirkham, W. B. 



'07 The maturation of the mouse egg. Biol. Bull., Vol. 12. 



4. Kirkham, W. B. 



'07 The maturation of the egg of the white mouse. Trans. Conn. Acad., Vol. 13. 



5. Lams et Doorme. 



'07 Nouvelles recherches sur la maturation, et la fecondation de 1'oeuf des 

 mammiferes. Arch, de Biol., T. 23. 



6. Long, J. A. 



'08 Some maturation stages of the mouse egg. Science, N. S., Vol. 27, No. 693. 



7. Long, J. A. 



'12 Studies on the early stages of development in rats and mice. No. 3 by 

 E. L. Mark and J. A. Long. The living eggs of rats and mice, with a 

 description of apparatus for obtaining and observing them. Univ. of 

 California Publications in Zoology, Vol. 9, No. 3. 



