PARTHENOGENETIC CLEAVAGE OF THE ARMADILLO OVUM. 57 



cells. At best they may be designated as cytoids. Other writers 

 who have studied similar conditions in mammals have referred 

 to the existence of multicellular conditions in which some cells 

 possess nuclei and others do not. I suspect that, were the truth 

 known, these fragments without nuclei would turn out to be of 

 deutoplasmic origin. Very commonly these cytoids in our 

 material form a pseudo-epithelial layer surrounding the true 

 cells, as in Figs. 3 and 5, or less distinctly in Fig. I. In other 

 cases they are distributed at random among the cellular products 

 of cleavage (Figs. 7-11) and serve only to give a false appearance 

 of cellular multiplicity and to confuse and obscure the pictures 

 of cleavage. 



THE REESTABLISHMENT OF NORMAL INTERRELATIONS BETWEEN 

 THE NUCLEUS AND THE CYTOPLASM AND THE RESULT- 

 ANT FORMATION OF CLEAVAGE SPINDLES. 



The egg, much reduced in size but with a renovated cytoplasm, 

 is now the seat of a renewal of nucleo-cytoplasmic exchanges, 

 as evidenced by the appearance of an extensive system of astral 

 rays at the two poles of the spindle. It will be recalled that the 

 nucleus during the period prior to ovulation was a naked spindle, 

 enclosed in an insulating capsule and entirely devoid of astral 

 radiations. Such a spindle is evidently an isolated system and 

 lies inert in the cytoplasm. The renovated cytoplasm of the 

 egg from which the deutoplasm has been extruded now bears a 

 different chemical relation to the nucleus and the change is 

 shown in the disappearance of the capsule about the nucleus 

 and in the appearance of typical astral radiations. That a 

 renewal of metabolic relations between nucleus and cytoplasm is 

 one of the most essential facts of normal fertilization has been 

 recently maintained by Lillie (1911) on the basis of his studies of 

 fertilization in Nereis, and there is reason to believe that this is 

 the physiological explanation of parthenogenesis wherever the 

 latter is found, whether normal or experimental. In this case 

 it is my conviction that the sudden change in the chemical 

 character of the cytoplasm restores the basis of life and growth 

 to the egg and that cleavage is the natural consequence. In 

 such cases as that shown in Fig. i the nucleus has returned to a 



