258 SOME ASPECTS OF CELL-CUEMISTRY AND CELL-PHYSIOLOGY 



fact that every part of the latter may show the characteristics of 



either or both parents. 



Boveri ('89, '95, i) has attempted to test this conclusion by a most 



ingenious and beautiful experiment ; and although his conclusions do 



not rest on absolutely certain 

 ground, they at least open the 

 way to a decisive test. The 

 Hertwig brothers showed that 

 the eggs of sea-urchins might 

 be enucleated by shaking, and 

 that spermatozoa would enter 

 the enucleated fragments and 

 cause them to segment. Boveri 

 proved that such fragments 

 would even give rise to dwarf 

 larvae, indistinguishable from 

 the normal in general appear- 

 ance and differing from the 

 latter only in size and in the 

 very significant fact that their 

 nuclei contain only half the nor- 

 mal number of chromosomes. 

 Now, by fertilizing enucleated 

 egg-fragments of one species 

 {Sph&rechinus grannlaris) with 

 the spermatozoa of another 

 (Echinus microtuberculatus), Bo- 

 veri obtained in a few instances 

 dwarf Plutei showing purely 

 paternal characteristics (Fig. 

 1 1 6). From this he concluded 

 that the maternal cytoplasm has 

 Fig. n6.- Normal and dwarf larvae of the no determining effect on the 



sea-urchin. [BOVERI.] offspring, but supplies only the 



A Dwarf Pluteus arising from an enucleated mate rial in which the sperm- 

 egg-fragment ot ^phcerechinus granularis, fertilized . x 



with spermatozoon of Echinus microtvberculatus, nucleus Operates. Inheritance 



and showing purely paten, al characters. B. Nor- j s therefore, effected by the 

 mal Pluteus of Echinus microtuberculatus. 1 



nucleus alone. 1 Boveri s result 



is unfortunately not quite conclusive, as has been pointed or.t 

 by Seeliger and Morgan, yet his extensive experiments establish, I 

 think, a strong presumption in its favour. Should they be positively 

 confirmed, they would furnish a practical demonstration of inheritance 

 through the nucleus. 



1 The rentrosome is left out of account, since it is frequently derived from one sex only. 



