Experiments on Aneroid Barometers and their Discussion. 401 



from the male and female nuclei respectively. Indications of the 

 first segmentation spindle are also to be observed at this stage as 

 fine staining threads running throughout both nuclei. No definite 

 resting fertilised nucleus is formed. 



The spindle, which lies obliquely in the centre of the egg, is at 

 first multipolar in form, and while it is in this condition the chromo- 

 somes begin to split longitudinally, but can still be distinguished 

 roughly into two groups. 



Only after the formation of four segmentation nuclei do these 

 begin to wander down to the base of the egg. On its way down 

 each nucleus has a distinct sheath of cytoplasmic fibres, but when it 

 reaches the base these become replaced by fine cytoplasmic threads, 

 which run from the nucleus out into the general cytoplasm. These 

 later-formed cytoplasmic; threads seem to be connected with the for- 

 mation of cell walls around the nuclei. 



The number of chromosomes in the egg nucleus was determined 

 by counting them in the division which cuts oif the ventral canal 

 cell, and was found to be twelve. The same number was also to be 

 found in the nuclei of the cells of the prothallial tissue and of the 

 pollen mother cells. The chromosomes of the first segmentation 

 spindle, on the one occasion on which they could be counted, were 

 exactly twenty-four in number. The chromosomes were also counted 

 in several types of sporophytic tissue ; at least twenty-one chromo- 

 somes could always be observed ; presumably twenty-four are always 

 present. 



No centrospheres or centrosomes were to be seen in connection 

 either with fertilisation or with any of the related processes. 



" Experiments on Aneroid Barometers at Kew Observatory 

 and their Discussion." By C. CHREE, Sc.D., L.L.D., F.R.S., 

 Superintendent. Received May 5, Read June 9, 1898. 



(Communicated by the Author at the request of the Kew Observatory Committee.) 



(Abstract.) 



The paper deals with two species of data. The first consists of 

 particulars derived from the records at Kew Observatory as to 

 the errors observed in about 300 aneroid barometers. These had been 

 subjected to the ordinary Kew test, which consists in lowering the 

 pressure to which the aneroid is exposed inch by inch to the lowest 

 point at which verification is desired, and raising the pressure in a 

 corresponding way to its original value. Readings are taken at 

 each inch of pressure during both the fall and the recovery, and a 

 table of corrections is obtained by reference to the corresponding 

 readings of a mercury gauge. 



