190 Prof. J. B. Farmer and Mr. J. LL Williams. 



and that when freed from the oogonium it exerted an attraction on 

 the antherozoids just like its larger sister oospheres. 



When an oogonial nucleus is about to divide, it first becomes 

 slightly, then very much, elongated so as to resemble an ellipse. 

 Fine radiations are seen to extend from the two ends into the 

 surrounding cytoplasm. The latter is at first tolerably uniformly 

 granular, but as the radiations around the polar areas increase, these 

 regions become cleared altogether of the granules which then become 

 massed outside them. The nucleus rapidly becomes more spindle- 

 shaped, and its chromatic elements are chiefly grouped near each 

 pole, leaving a clear space about the equator in which the nucleolus. 

 is situated. In this respect the nuclei of Fucus offer a striking con- 

 trast to those of Pellia epiphylla already described (* Annals of 

 Botany,' vol. viii, p. 221) by one of us. In the latter plant the 

 chromatic portion of the nucleus assumes an equatorial position at 

 the corresponding stage in division, whilst the polar regions are clear. 



The polar radiations continue to increase and the nucleus to- 

 lengthen, until the entire structure recalls the figure of a dumb-bell, 

 in which the nucleus answers to the handle, and the radiation areas 

 to the knobs. If the radii be traced outwardly, they are seen to 

 terminate either in the frothy protoplasm, on the angles where the 

 foam walls meet, or on the large granules which surround the cleared 

 areas and are embedded in the foam. This point is one of 

 considerable importance, and we shall revert to it further on. 

 No structures were seen which could certainly be identified as 

 centrosomes, although bodies suggestive of them were often observed ; 

 but these proved to be so variable in size and position, as well as in 

 number, that we feel unable to attach any special significance to 

 them. 



The next stage in the mitosis is that in which the interpolar 

 spindle arises, with the chromosomes disposed upon its equator. 

 The spindle is very remarkable inasmuch as it is entirely intranuclear, 

 somewhat resembling that described by Fairchild for Valonia, or by 

 Harper for Peziza. The nuclear wall can be distinguished until 

 quite late in karyokinesis, and it is possible that no complete 

 mingling of the cytoplasm with the contents of the nucleus takea 

 place here. The spindle is extremely clear, and in several prepara- 

 tions, owing to a fortunate contraction during manipulation, the 

 ends of the nuclear part of the spindle also had broken away from 

 the cytoplasmic poles, and were visible as clean conical structures 

 forming the poles of the nuclear spindle. The chromosomes were 

 too minute to admit of their development being satisfactorily studied, 

 but in all the oogonial spindles their number was estimated at ten 

 when seen arrayed on the spindle equator. They were only seen in 

 profile, and consequently it was difficult to be sure whether there 



