152 A. RICHARDS. 



distinctly. An equatorial plate is not usually formed as the 

 chromosomes pass to the poles irregularly. Figs. 53 and 54 

 illustrate these facts. 



The reconstruction of the female pronucleus is shown in Fig. 

 55. These stages suggest amitotic division of the ovum some 

 more than that figured; their true nature, however, is readily 

 ascertained. 



I am unable to see that the maturation of Moniezia has any 

 bearing whatever on the "hypothesis of individuality" of chro- 

 mosomes, which Child says these mitoses do not appear to 

 strengthen, for it does not seem to me that evidence either pro 

 or con is presented here. Indeed, the whole question involved 

 is not so much whether the chromosomes maintain their indi- 

 viduality as it is whether the mechanism of division will give 

 an exact sorting of the male and female elements in the germ 

 cells or a mere separation of unequal parts of the nuclei. If 

 mitosis could be established as the universal method of cell 

 division that fact alone would by no means warrant the assump- 

 tion of chromosome continuity, as Child would seem to imply 

 that it would do. Among those who believe that mitosis will 

 be found general in germ cells are many who do not accept the 

 individuality hypothesis as it is now put forward. Furthermore, 

 proof of that hypothesis will demand observations upon a more 

 favorable object than Moniezia. I would emphasize the fact, 

 therefore, that Moniezia presents no evidence upon the indi- 

 viduality hypothesis. 



Cleavage. The steps of the cleavage process in Moniezia were 

 discussed in 1881 by Moniez from an embryological point of view, 

 and by Child in 1907 from the point of view of cell division. 

 The results of Moniez are very suggestive and deserve to be 

 repeated in the light of more recent discoveries on cleavage and 

 with later methods of technique. Since the cleavage of Moniezia 

 is deserving of this broader treatment I shall not here attempt 

 other than the most general statement of the process but shall 

 concern myself with the method by which segmentation is ac- 

 complished. 



The type of cleavage, as will be seen from a glance at the fig- 

 ures, from 56 on, is that of a large macromere giving off small 



