THE OVUM OF THE NINE-BANDED ARMADILLO. 125 



of many examples of parthenogenetic cleavage it now appears 

 that this spindle in no way resembles a cleavage spindle, for 

 the egg is not in a condition for cleavage, in that the deutoplasmic 

 mass is still an integral part of it. The only alternative expla- 

 nation that occurs to me is that we have here a rare case of a 

 continuation one step further than is normal of the processes 

 involved in maturation. The spindle in this egg is as perfect 

 as any polar spindle observed in my material and contains 

 without question 16 chromosomes. It is a naked central spindle 

 without any traces of the aster radiations characteristic of true 

 cleavage spindles. As though in physiological sympathy with 

 the egg cell both polar bodies are seen to have proceeded somewhat 

 further in their development than those in any other egg observed. 

 The first polar body has completely divided into two ootids, 

 and the second polar body, which is very large and well-formed, 

 shows a polar view of a mitotic spindle, homologous with that 

 seen in the egg itself, and has likewise 16 chromosomes. This 

 curious egg was found in a follicle like that shown in Fig. 12, 

 in which the process of atresia had made noticeable progress. 

 The case is unique in the annals of biology and may possibly 

 be explicable on some other basis than that which I have sug- 

 gested. Personally I see no alternative explanation. 



XII. FERTILIZATION. 



Although diligent search has been made through large numbers 

 of ovaries with fallopian tubes attached, only one tube egg has 

 been found. This one egg, however, is so evidently a normal 

 example of the conditions typical for the species that it warrants 

 a detailed description. The egg is found in a part of the fallopian 

 tube just where it straightens out in its course toward the uterus. 

 It lies free in the tube surrounded by a coagulum of material 

 evidently composed of the disintegrated fragments of granulosa 

 cells. It runs through twelve serial sections of 10 microns 

 thickness and is therefore about .12 mm. in diameter, or a 

 little smaller than the average full grown ovarian ovocyte. The 

 zona is well defined and unbroken. The two polar bodies, each 

 with its nucleus in a resting phase, are situated in contact with 

 the formative protoplasm at some distance from the pronuclei. 



