390 PROGRESS OF SCIENCE IN THE CENTURY. 



() 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 cytoplasm ic. 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 (6) the mingling of heritable characteris- 

 tics as two distinct processes in fertilisation. 



In the following year, Delage extended his experi- 

 ments,! and showed that a non-nucleated fragment 

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

 lusc (DenlaUum}, and of a worm (Lantce) may be 

 effectively fertilised and give rise to a Pluteus, a 

 Veliger, or a Trochophore larva respectively. He 



Comptct Rentfut Acad. ffd., Parit, CXXVII.. 1898. pp. 

 528-631. 



t Archive Zoolopie Experimental*. VII. (1899), pp. 383- 

 417, 11 flgs. 



