77 



I think, necessary at the present time, in oixler to decide 

 ■whether in any given case the numerous small bodies in the 

 protoplasm should be looked upon as nuclei — in the same sense 

 in which we speak of them in the higher plants and animals — 

 to show that they have some perfectly definite structure which 

 distinguishes them from the other bodies in the protoplasm. 



Perhaps the most important factor in the determination of 

 this question lies in the division of the nucleus : where this is 

 indirect or karyokinetic we have the most satisfactory proof of 

 the nuclear nature of the body in question. It is not necessary 

 that the changes which take place during this karyokinesis 

 should be so complicated or so numerous as those which take 

 place in the higher plants. It is sufficient if we are able to 

 recognise that the division is one which conforms to some simple 

 generalisation in wliich the changes- which take place in the 

 nuclei of the higher plants are included. In the nuclei of the 

 higher plants we can, roughly speaking, recognise two distinct 

 constituents in each nucleus : one which is capable of becoming 

 stained deeply by aniline dyes, and another which remaiiis 

 unstained. The former is called chromatin the latter achromatin. 

 When the division of the nucleus takes place, it does so in 

 such a manner as to bring about the separation of tlie chromatin 

 into two equal — or in some cases perhaps even unequal — parts, 

 each of which becomes a perfect nucleus. 



Tlie changes which take place may be summed up as follows. 

 The chromatin breaks up into a number of isolated parts of 

 characteristic form, which may be called the chromatic elements. 

 These become arranged in the median plane of the nucleus 

 between its two poles ; they then divide into two halves, one of 

 which goes to either pole, and there they become transfoi'med 

 into the network of two new nuclei. This process of division 

 is known as karyokinesis. 



So far as I am aware, two observers only have made 

 researches upon karyokinesis in the nuclei of the Fungi. 

 Rosenvinge* has obtained indications of it in certain Agaricinea?, 

 but was not able to demonstr^e it satisfactorily ; and Hartog'^ has 

 recently shown that some of the phenomena of karyokinesis 



* Anil, des Sci. Nat. , Serie YII. , tome iii. 

 '' Hartog — Recherches sur la Structure des Saprolegni^es. 



