188 THE CONTINUITY OF THE GERM-PLASM AS THE 



of great and even of fundamental importance. Furthermore, the 

 observations, conducted last year by van Beneden, on the process 

 of fertilization in Ascaris, have given to Flemming's discovery a 

 clearer and more definite meaning than could have been at first 

 ascribed to it. The discovery proves, in the first place, that the 

 nucleus always divides into two parts of equal quantity, and fur- 

 ther that in every nuclear division, each daughter-nucleus receives 

 the same amount of nuclear substance from the father as from the 

 mother ; but, as it seems to me, it is very far from proving that the 

 quality of the parent nucleoplasms must always be equal in the 

 daughter-nuclei. It is true that the fact seems to prove this ; and 

 if we remember the description of the most favourable instance 

 which has been hitherto discovered, viz. the process of fertilization 

 in the egg of Ascaris, as represented by van Beneden, the two 

 longitudinal halves of each loop certainly impress the reader as 

 being absolutely identical (compare, for instance, loc. cit. Plate XIX, 

 figs, i, 4, 5)- But we must not forget that we do not see the 

 molecular structure of the nucleoplasm, but something which we 

 can only look upon (when we remember how complex this molecular 

 structure must be) as a very rough expression of its quantity. Our 

 most powerful and best lenses just enable us to make out the form 

 of separate stainable granules present in a loop which is about to 

 divide : they appear as spheres and immediately after division as 

 hemispheres. But according to Strasburger, these granules, the so- 

 called microsomata, only serve for the nutrition of the nuclear sub- 

 stance proper, which lies between them unstainable, and therefore 

 not distinctly visible. But even if these granules represent the true 

 idioplasm, their division into two exactly equal parts would give us 

 no proof of equality or inequality in their constitution : ft would 

 only give us an idea of their quantitative relations. We can only 

 obtain proofs as to the quality of the molecular structure of the 

 two halves by their effect on the bodies of the daughter-cells, and 

 we know that these latter are frequently different in size and 

 quality. 



This point is so important that I must illustrate it by a few more 

 examples. The so-called polar bodies (to be treated more in detail 

 below) which are expelled during maturation from the eggs of so 

 many animals, are true cells, as was first proved by Biitschli in 

 Nematodes : their formation is due to a process of undoubted cell- 



