1 86 J. THOMAS PATTERSON. 



position, but also because they are apparently bivalent. They 

 are not tetrads in shape, as in the characteristic condition of the 

 first maturation, yet that they are the egg chromosomes and 

 not those of the sperm is evidenced by the fact that the sperm is 

 located in another part of the ovum. 



The peculiar behavior of this karyokinetic figure is not con- 

 fined to the chromatin; the centrosomes frequently present unique 

 conditions. It is not uncommon to find the centrosome at one 

 or both ends of the spindle undergoing division, but this would 

 not be striking since in many germ cells, both male and female, 

 a precocious division occurs were it not for the fact that at 

 one end the axis of the two centrosomes is at right angles to 

 that of the spindle, while at the other end it is simply a continu- 

 ation of the spindle axis. The precocious division of the cen- 

 trosome frequently results in the formation of a double aster. 



I have not been able to follow with certainty all of the sub- 

 sequent steps in the. history of this spindle, but the end result 

 in all cases would seem to be a return to a sort of resting stage 

 on the part of the nucleus. It differs from the corresponding 

 stage of Thysanozoon Diesingii, in that the nucleus instead of 

 being a large vesicle, appears in the form of four vesicles, one 

 for each chromosome (Fig. 19). These may be more or less 

 grouped together or widely separated, but they later come to- 

 gether and_ fuse, producing a lobulated nucleus which retains 

 this condition until the onset of maturation (Fig. 21). It will 

 be seen from this rather brief account that the only function 

 which one might assign to the aborting spindle in G. gemellipara 

 is that of scattering the chromosomes in the form of vesicles; 

 but since these are later collected together into a single vesicle 

 before maturation, it is difficult to attach any real significance to 

 this whole peculiar phenomenon. Inasmuch as several odd con- 

 ditions have been observed, both in the centrosomes and the 

 chromosomes, it is not at all improbable that the aborting spindle 

 is an abnormal display. But it can not be the result of placing 

 the animals under unfavorable conditions because the spindles 

 are found in worms killed immediately upon their removal from 

 the moll use. 



It should be pointed out here that Graffilla is not a favorable 



