228 WHITMAN'. ' [Vol. I. 



they influence or react upon each other, are questions still 

 awaiting-decisive answers. The natural boundary line between 

 the two, at first clearly defined, begins to fade almost simul- 

 taneously with the earliest appearance of kinetic changes, be- 

 comes rapidly effaced as the energy of display increases, and is 

 resumed only at regularly recurring epochs, when outward 

 manifestations of activity cease. Under such conditions, with 

 karyoplasm passing uninterruptedly into cytoplasm, it is cer- 

 tainly very difficult, and perhaps quite impossible with the 

 micrographical means at our command, to determine precisely 

 the part played by each. 



The majority of writers are inclined to seek \\\e pj'imum mobile 

 in the nucleus, and to make the nucleus responsible for the kinetic 

 phenomena displayed in the cytoplasm. Attempts have been 

 made to settle this question . experimentally, through the arti- 

 ficial division of infusoria; but thus far no one has undertaken 

 a critical analysis of the phenomena of maturation and impreg- 

 nation, with a view to finding test cases. It is this side of the 

 subject which I propose to consider in the present paper. 



It may be noticed, first of all, that the phenomena in ques- 

 tion are not all of an active nature. Some are plainly induced 

 by outside influences, or are simply secondary effects resulting 

 from altered internal conditions. The rapid clearing up of a 

 pelagic fish Q%'g the moment it comes in contact with water, 

 owing to the dissolving of its opaque granules, is an example 

 of this kind. All changes in the relative position of the con- 

 stituent elements of the egg that result from differences of 

 specific gravity may be referred to the same category. We 

 have, then, to distinguish between active and passive changes, 

 and the latter can be set aside as unimportant to the inquiry. 

 The former may be conveniently divided into two classes, one of 

 which I shall designate cytokinetic, in distinction from the other, 

 which is now generally called, after Schleicher's example, 

 karyoJdnetic} 



' The term karyokinesis has been objected to by Flemming (Zellsubstanze, Kern 

 und Zelltheilung, p. 376) as neither describing the form nor indicating the nature of 

 nuclear metamorphoses. Karyotnitosis, or simply tnitosis, is the substitute proposed 

 by Flemming. Priority and general usage are in favor of karyokinesis ; besides, this 

 term commends itself, in my opinion, as the simpler and more comprehensive, and as 

 expressing better the essence of the phenomena. Its leading idea is motioji, but 

 motion viewed as an exponent of forces residing in, or acting upon, the nucleus. It 



