32 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



that the nuclei are usually vesicles. Rollett* some time ago paid 

 particular attention to the nuclei of the corpuscles, and described 

 a peculiar formation of vacuolse in their interior. More re- 

 cently it has been stated, on the authority of observations 

 made in his laboratory, that after induction currents have 

 been applied to the corpuscles the nuclei will coalesce, which 

 is very unlikely on the supposition that they consist of 

 vesicles. 



Our knowledge respecting the chemical characters of nuclei 

 is also very obscure. Kiihnef states that it is probable they 

 contain an albuminous substance, and it is known that they 

 present considerable resistance to the action of acids and al- 

 kalies ; but this furnishes us with no satisfactory information 

 respecting their physiological significance or chemical compo- 

 sition. Briicke remarks that the consistence of the nucleus is 

 peculiar. On the cell theory it is believed to constitute the 

 primary solid constituent of the cell, though no absolute 

 proof has been obtained on the point. It cannot be denied 

 that the nucleus is originally of very soft consistence, and 

 that it subsequently becomes denser ; nor can it be admitted 

 that it ever exhibits any considerable degree of resistance in 

 young cells. 



It has been stated that, in all probability, the nucleus of the 

 fecundated egg disappears. It is equally probable that the 

 nucleus of the first segmentation mass is a new formation. 

 But, as we possess no precise investigations respecting the dis- 

 appearance of the germinal vesicle, we are also unable to 

 derive the first nucleus of the segmentation mass of the egg of 

 the frog from the nucleus of the unfertilized egg. In the unferti- 

 lized egg we meet with a vesicular nucleus. Under a strong 

 lens it may easily be torn with needles, and then the membrane 

 becomes apparent. The small sacculus contains a little clear 

 fluid and a few granules. The first nucleus of the segmenta- 

 tion sphere is, however, a completely homogeneous and appa- 

 rently soft spherical body. 



When it is said that the nuclear vesicles undergo solution, 



* Versuche am Blute, Wiener Sitzungsberichte, 1863. 

 t Lehrbuch der Physiologische Chemie. Leipzig, 1867. 



