390 PROGRESS OF SCIENCE IN THE CENTURY. 



(i) Delage's Experiments. In a short paper 

 entitled " Embryos without Maternal Nucleus/' 

 Professor Yves Delage described in 1898 * a remark- 

 able experiment, implying a very delicate operation. 

 He divided the egg of a sea-urchin under the micro- 

 scope into two parts, one containing the nucleus and 

 the centrosome, the other simply cytoplasmic. Be- 

 side them he placed an intact ovum, and then let 

 spermatozoa in. All the three objects showed equal 

 " sexual attraction," all were " fertilised," and all 

 segmented, the intact ovum most rapidly, the nucle- 

 ated fragment more slowly, the non-nucleated frag- 

 ment more slowly still. In one case, the develop- 

 ment proceeded for three days ; the intact ovum had 

 become a typical gastrula (two-layered embryo), 

 the nucleated fragment a smaller gastrula, and the 

 non-nucleated fragment also a gastrula, but with a 

 very much reduced cavity. The experimenter there- 

 fore concluded that fertilisation and some measure 

 of development may occur in a fragment of ovum 

 without a maternal nucleus; and he was led to dis- 

 tinguish between (a) the stimulus given to the ovum 

 by something which the spermatozoon brought to 

 it, and (&) the mingling of heritable characteris- 

 tics as two distinct processes in fertilisation. 



In the following year, Delage extended his experi- 

 ments,f and showed that a non-nucleated fragment 

 of the ovum of a sea-urchin (Echinus), of a mol- 

 lusc (Dentalium), and of a worm (Lanice) may be 

 effectively fertilised and give rise to a Pluteus, a 

 Veliger, or a Trochophore larva respectively. He 



* Oomptes Renclus Acad. Sci., Paris, CXXVII., 1898. pp. 

 528-531. 



t Archives Zoologie Exptrimentale, VII. (1899), pp. 383- 

 417, 11 figs. 



