32 SEGMENTATION AND FORMATION OF THE LAYERS. 



seen in section) are rather larger than in the protoplasm imme- 

 diately around the nucleus. 



The most important, and at tlie same time most certain, of 

 these observations on the nucleus of the fertilised ovum of 

 Peripatus, is that the intra-nuclear and extra-nuclear reti- 

 culum are both continuous with the so-called nuclear mem- 

 brane. This continuity between the extra- nuclear and nuclear 

 spongework is rendered still more obvious by a consideration 

 of the next form. 



d. The last form I have to describe under this head is the 

 spindle form (PL III, fig. 11). It was met with in an ovum 

 of two segments. 



The spindle is of enormous size (distance between the poles 

 0'06 mm.). The protoplasmic fibres composing it are abso- 

 lutely the same in appearance as the rest of the cell proto- 

 plasm, from which they must have been largely derived. 

 The chromatin is present in a very condensed form (i. e. deeply 

 staining) as a number of bent rods at the equator of the 

 spindle. Around the poles of tbe spindle the protoplasmic 

 reticulum is arranged in a radiate fashion. The spindle 

 appears not to be composed of simple fibres running from pole 

 to pole, but of the ordinary reticulum, the meshes of which are 

 very much elongated in a direction parallel to the long axis of 

 the spindle. The same may be said of the fibres radiating from 

 the poles of the spindle. 



The facts which are most clearly brought out by the above 

 observations, and about which I have no doubt, are — 



1. The continuity of the nuclear reticulum with the extra- 

 nuclear reticulum. 



2. The similarity in structure between, and, the continuity 

 of the so-called fibres of the spindle in form d with the sur- 

 rounding reticulum; and the conclusion I have drawn from 

 my observations is, that the nucleus of the fertilised ovum of 

 Peripatus diflFers from the cell protoplasm only in the manner 

 in which the so-called chromatin contained in the proto- 

 plasmic meshwork (both of nucleus and rest of ovum) behaves. 

 In the nucleus it varies from a state of diflfusion through the 



