ARTIFICIAL PARTHENOGENESIS AND FERTILISATION. 479 



Artificial Parthenogenesis and Fertilisation : 

 A Review. 



By 

 Thomas If. Brycc. 



. This ai'ticle is an eifort to gather together, in so far as they 

 relate to the phenomena of fertilisation in the sea-urchin 

 egg, the results obtained by experiments. It does not pre- 

 tend to consider the problem of fertilisation as a whole, nor 

 the phenomena save in Echiuoderms, and no attempt will be 

 made to establish comparisons with other forms in which the 

 details may to some extent differ. The limitation to one form 

 is in so far appropriate, that practically all the experiments 

 have been made on Echiuoderin eggs. 



I have personally studied fertilisation in the egg of Echinus 

 esculentus — specially in sections, — and though I have 

 nothing fresh to add to the description of the facts, this 

 article may in a measure be considered a sequel to a paper 

 on maturation in the same form. In that paper my attention 

 was chiefly directed to the chromosomes, and I did not follow 

 out the results of observers in the experimental field, but 

 as some of the phenomena described are of interest in con- 

 nection with these results, I shall take the opportunity of 

 returning to them. 



The two mitotic divisions characteristic of the maturation 

 phases, differ markedly from those which take place in the 

 segmentation phases. In many respects there is a close 

 resemblance to phenomena observed in the eggs of Toxo- 

 pneustes, which develop parthenogenetically under the 

 influence of magnesium chloride solution (Wilson, 1901). 



VOL. 46, r-AKT 3. — NEW SERIES. G G 



