200 section c. invertebkata. 



3. Fertilisation of the Egg of Rhynchelmis. 

 By Prof. F. Vejdovsky. 



Prof. Vejdovsky of the University of Prague spoke on certain 

 phenomena in the fertiHsation of the egg of Rhynchelmis, the 

 centrosome of which undergoes very compHcated changes which 

 were demonstrated by a series of beautiful microscopical prepara- 

 tions. He said : 



In a preliminary note, which will be published in the " Sitzungs- 

 ber. kon. bohm. Gesellsch. der Wissenschaften" for the year 1898, 

 I have in collaboration with my assistant A. Mrdzek announced 

 the results of the new researches on the dynamic elements in cell- 

 division, known as " centrosome " {Boveri), " corps central " {E. Van 

 Boieden), and "periplast" {Vejdovsky). The morphological signifi- 

 cance of these bodies is up to the present time disputable, although 

 it is certain that they originate from the spermacytoplasma. 



In most, if not in all cases, the " centrosome " is surrounded 

 with a hyaline sphere, the " sphere attractive " of E. Van Beneden. 

 In my nomenclature the sphere is designated as "mother-periplast" 

 and the " centrosome " of Boveri as " daughter-periplast." I have, 

 that is to say, in opposition to Boveri and E. Van Beneden demon- 

 strated that the dynamic body for the next cell-division — the 

 daughter-periplast — originates in the centre of the sphere of the 

 preceding division, or in the mother-periplast. 



In our present researches on the fertilization and division of the 

 ova of Rhynchelmis we are able to confirm my old interpretation, 

 that the so-called " sphere attractive " is the increased daughter- 

 periplast or the centrosome of Boveri. The ova of Rhynchelmis 

 are the most favourable material to solve the question, the division- 

 bodies being of such a size, that it is possible to recognize them 

 with the naked eye. 



I shall now demonstrate a series of some successive stages of 

 fertilization and division of these eggs, the results of which are as 

 follows : 



(i) The division-element in the Q^a of Rhynchelmis is a very 

 small, punctiform corpuscle ; it is not identical with the centrosome 

 of Boveri, nor with the " corps central " of E. Van Beneden, corre- 

 sponding only to the so-called " centriole." Notwithstanding this 

 we designate it as centrosome. In the primitive state the corpuscle 

 occupies the centre of a great sphere, the mother-periplast. 



(2) In the period of fertilization, when the female pronucleus 

 meets with the male one, our centrosome is surrounded by a small 

 hyaline sphere, which I designated twelve years ago as daughter- 

 periplast. It is probable that the sphere originates from the 

 changed peripheral stratum of the centrosome, the last being 

 smaller than in the preceding stage. 



