CELL DIVISION IN T.KNIA. 



317 



lar character of the chromatin and linin is clearly shown with 

 Kernschwarz and Lichtgriin. This description answers not only 

 for late oogonia but also for the early ones and for the oocytes. 

 Fig. 9 is an early oogonium. 



Fig. 10 illustrates the early condition of the spirem stage. 

 Oogonia in this stage and slightly later are very numerous in 

 certain lots of material. In other lots I find many resting 

 stages. Anaphases and telophases, too, are not difficult to find 

 but metaphases are conspicuously absent. This probably means 

 that the metaphases are of short duration. It also indicates 

 a fact which I believe to be very pertinent to the question of 

 the frequency of mitoses; namely, a periodicity 1 with regard to 



FIG. 9. Resting oogonium with a definite chromatin reticulum ; no " Nebendot- 

 ter " present. 



FIG. 10. Oogonium ; very early prophase, spireme formation beginning. 

 FIGS. 9-17. From cells stained with Kernschwarz and Lichtgriin. 



the divisions. It is well known that physiological factors may 

 govern the time of mitotic divisions. A case in point is that 

 recently described by Beckwith, previously mentioned ; likewise, 

 in certain insects and in many plants mitosis occurs at night only. 

 The fact that many nuclei from one lot are in the same stage of 

 division indicates, I believe, the effect of some physiological factor. 

 What that factor is, I can only conjecture. Perhaps mitotic 

 periods may occur only after a more or less prolonged fast on 

 the part of the host, for then the energies of the parasite are not 

 directed towards the assimilation of food. 



During the maturation period the regular course is followed. 



1 This expression is not intended to imply that a definite amount of time intervenes 

 between successive periods ; they may recur at irregular intervals depending on some 

 physiological factor. 



