9^ REMARKS ON CERTAIN [XI. 



Since then I have made the attempt to fertilize the ovum 

 of a frog w^ith the nucleus of another ; the experiment did not 

 succeed, and we could scarcely expect it to do so, considering 

 the very considerable amount of injury caused by transferring 

 a nucleus into another ^gg. 



Boveri ^ has been more fortunate ; for he succeeded in finding 

 an object which permitted the converse of my experiment. 

 Adopting the method of R. Hertwig, he separated, by shaking, 

 the nucleus from the ovum of an Echinus, and succeeded in 

 rearing such denucleated eggs by the introduction of sperma- 

 tozoa. A regular segmentation nucleus was formed from the 

 spermatozoon which penetrated the &gg, embr3^ogeny followed 

 its usual course, and the &gg gave rise to a perfect but rather 

 small larva, which swam freely about in the water, and lived 

 until the seventh day. 



This experiment is by itself sufficient to prove that the views 

 on fertilization adopted b};- Strasburger and myself are correct, 

 viz. that the nucleus of the spermatozoon can pla}^ the part of 

 the nucleus of the ^gg^ and vice versa, and that the older view 

 to w^hich Professor Vines ^ adheres, must be given up. 



An interesting and important modification of Boveri's ex- 

 periment, affords further support to the results obtained by 

 him, and confirms — if indeed confirmation be necessar}^ — the 

 view which looks upon the nuclear substance as idioplasm, as 

 maintained by O. Hertwig, Strasburger, and mj^self ^. 



If the eggs of Echinus niicrotubercitlatus, artificially deprived 

 of their nuclei, be fertilized, not with the spermatozoa of their 

 own species, but with those of another, Sphaerechinus granularis, 

 larvae are developed with the true characters of the last species only, 

 that is to say, nothing is inherited from the mother but every- 

 thing from the father. The nuclear substance is the sole bearer 

 of hereditary tendencies and by it the cell is governed. 



I have explained the first polar body of the metazoan egg 

 as the carrier of ovogenetic idioplasm which must be removed 



^ Boveri, ' Ein geschlechtlich erzeugter Organismus ohne miitterliche 

 Eigenschaften.' Gesellsch. f. Morph. u. Physiol. Munchen, i6 Juli, 

 1883. 



^ S. H. Vines, * Lectures on the Physiology of Plants.' Cambridge, 

 1886, pp. 638 681. 



^ Cf. Kolliker, ' Die Bedeutung der Zellenkerne fur die Vorgange der 

 Vererbung.' Z. f. W. Z. Bd. 42, 1885. 



