TRANSACTIONS OF SECTION D. i 1 



elements, four are rejected wltli the first globule, without undergoing any change ; 

 two with the second. Only two therefore remain for the actual nucleus of the egg. 

 At no stage therefore is there any division ot the nucleinic rods, whether longitu- 

 dinal or transversal, nor any clearing of the nuclein. On all these points O. 

 Zacharias supports me in opposition to E. van Beneden. 



Still we differ on a iew details. 



(a) According to Zacliarias, the AVagnerian spot, which is at first single and 

 homogeneous, divides into two parts, which are likewise homogeneous, and in each 

 of which later on chromatic globules appear. AVe cannot admit these assertions. 

 The nucleus of the young eggs is an ordinary nucleus, and in which the uucleinic 

 thread gives birth to eight rods, forming two quarternary groups. The apparent 

 homogeneity of the AVagueriau spot is invariably the result of bad treatment in the 

 preparation. As for the presence of globules instead of rods, it is the effect of the 

 leageuts or of the position of the rods as seen by the observer ; that is quite certain. 

 I have always maintained these various points in whatever I have published. My 

 •opponent admits moreover that the two spots are not nucleoles in the sense in 

 which Zacharias takes them (I call them plasmatic nucleoles) ; but without coming 

 to any decision on their nature, he gives them the name of ' mitoblast.' I had 

 showu that they were ordinary nucleinic nucleoles — the name ' mitoblasts ' is there- 

 fore needless, and as such should be rejected. 



(i) Zacharias did not notice any asters in the first figure. This may have been 

 perhaps from his having only seen our compressed figures, for usually the presence 

 of asters, oftentimes well developed, is unquestionable. 



(c) According to Zacharias, half the globules of each nuclear group are dis- 

 charged with the polar globules. AMien the groups are very close together it is 

 more diificult to come to a decision ; but when the figures are well opened or 

 ruptured it is ascertained that one of the groups is discharged and that the other 

 remains in the egg. ^Moreover, the only essential point is that six of the primitive 

 ■elements are expelled in toto. 



2. Boveri admits the existence of two Wagnerian spot.s, but according to him 

 these consist of a thick single prismatic rod, and are consequently homogeneous. 



These rods would undergo a binary division at the equator of each figure, and 

 the halves would withdraw to the poles. The exterior group is then expelled with 

 the globule. We must reject these assertions. The two primitive rods do not 

 •exist. They are undoubtedly formed of four distinct rods, which are blended, 

 owing to Boveri's imperfect preparations. His supposed equatorial division is then 

 but an illusion, as the eight rods have always been distinct. A 8 for their motion 

 towards the poles, I have never noticed it in the Ascaris Megalocephala. The first 

 spindle disappears, and Boveri seems in this to be at one with me. The separating 

 spindle is consequently distinct from the first. However, in other species I have 

 studied the polar ascent really takes place, and the separation of the polar globule 

 sometimes occurs in the kinetic spindle itself. It would not at all astonish me to 

 come across these characteristics in some varieties of the Ascaris of the horse. I do 

 not intend to treat of the normal form of the figure : that question was treated, e.r 

 profesHo, in the ' appendix ' to my lecture given at Brussels on March 5, 1887. 



II. Fecimclntioii .—^\xss\>9i\xm contends that the two fusing nuclei always fuse 

 in the centre of the egg. E. van Beneden contends that the fusion never takes 

 place before the figure of segmentation is formed. These two opinions are too 

 absolute. I have shown that this fusion sometimes takes place, sometimes does 

 not. As regards the fact itself, Zacharias and Boveri side with me. The former 

 of these two savants seeks to explain this difference. In his opinion, when the 

 figure is formed without previous fusion of the nuclei, the fusion had already taken 

 place at the top of the egg, and the result has been two hermaphrodite nuclei. 

 We do not think that is' the case. In fact, his figures, 10 to 13, Plate IX., 

 showing this fusion, have left me in doubt, for I have come across a number of 

 similar figures during my investigations, but the male nucleus, which it is difficult 

 to make out at that stage of its evolution, was still in the centre of the egg ; it was 

 therefore not in a fair way of fusing with the female element. The figure of the 

 top of the egg simply represents the female nucleus in which the primitive reds 



