314 THE AMERICAN MONTHLY [Nov., 



no satisfactory view was obtained. In tlie nuclei of embryo 

 kittens tbe chnHiiosonies are short and thick, and in the haema- 

 toxylin cnijtUiyctl took a very tlecp sUiin, in many cases almost 

 black. For these reasons it was usually impossible to distin- 

 guish individual chromosomes in either the monaster or dyastcr 

 staj;e but the ends of the chromosomes were usually distinct. 



The achromatic spindle at this stage is fairly conspicuous and 

 well delined. The chromosomes are seen clustered in the })lane 

 of the equatorial plate, while on both sides the fibrils of the 

 achromatic spindle converge to the pole corpuscles. From each 

 pole corpuscle, radiating out into the cytoplasm, are to be seen 

 the exceedingly delicate rays of achromatic substance, forming 

 the polar cones. Many nuclei were seen at this stage presenting 

 the appearance of the conventionalized diagram, such as that in 

 Quain's Anatomy, tenth edition. Vol, 1, Part II, figure 214, ex- 

 cept that tiie cliromosomes are not so distinct as in the diagram. 



In the process of metakinesis all phases were seen, from that 

 in which the limbs remained in contact while the apices of the 

 loops had separated, to the complete dy aster stage. In some 

 instances the ends of the limbs of two or four chromosomes re- 

 niaiu in contact, the others having separated. In nuclei in 

 which the two sets of chromosomes have migrated for some dis- 

 Umce, and are separated l)y an interval equal to the average 

 diameter of a resting nucleus, the exquisitely fine webs that 

 stretch from the ends of the limbs of one set to the ends of the 

 limbs of the other set may be seen in many instances. When 

 the two sets are separated by a small interval the web is not eas- 

 ily seen. 



In the dyaster stage tiie two sets of chromosomes do not pre- 

 sent the appearance that is usually represented. As stated be- 

 fore the chromosomes of the cat are short and thick, and the 

 limbs do not extend in such a way as to make it easy to deter- 

 mine their number. It is stated that the nuclei of each species 

 contain a definite number of chromosomes. From what can be 

 determined in the nuclei under observation, each set of chro- 

 mosomes in the dyaster stage contains four chromosomes, al- 

 though it is difficult to determine this point with certainty. 



The portion ofthe achromatic spindle between the pole corpus- 

 cles and the two sets of chromosomes can be made out easily, as 

 the delicate webs are quite conspicuous in the dyaster stage, and 



